Markets opened in negative territory on Friday morning as eyes turned to the all-important reading of first-quarter economic growth in the US.The US Commerce Department is expected to reveal later on that gross domestic product (GDP) in the world's largest economy expanded at a 3.0% pace in the first three months of 2013, a sharp acceleration from the meagre 0.4% growth in the final quarter last year.However, according to Senior Market Analyst Michael Hewson from CMC Markets, "this seems excessively optimistic given that we have seen payroll tax hikes and spending cuts kick in at the beginning of the year as well as a host of disappointing economic data for March".He said: "We've seen a disappointing ADP private and non-farm payrolls report, as well as a plunge in consumer confidence, a surprise slide in US retail sales and a really poor durable goods number, as well as some weaker housing data, which all suggest that we could see a significantly sub 3.0% read."Also a cause for concern this morning were comments from Jens Weidmann, the head of Germany's Bundesbank. In a report dated in December but published Thursday by Handelsblatt, he raised issues with the European Central Bank's Outright Monetary Transactions programme, saying it could devalue the sovereign debt of participating nations.Growth figures from the UK yesterday showed that Britain had easily avoided a triple-dip recession in the first quarter, with GDP growing by 0.3% owing to strength in the services sector. While this was better than the 0.1% expansion expected by analysts, markets gave a rather mixed reaction given that the upside surprise would likely prompt the Bank of England to refrain from injecting more stimulus for the time being.Miners provide a drag early onHeavyweight mining stocks were in the red in early trading as risk appetite declined ahead of the US. ENRC, EVRAZ, Rio Tinto, Anglo American, Fresnillo, Antofagasta and Glencore were among the worst performers.Business process management provider Capita was a high riser after saying that it will form a joint venture company with the UK Cabinet Office to commercialise the government's portfolio of best management practice training tools.Pearson, the publishing and education business, edged higher despite saying that first-half profits would likely be lower than last year as it starts to phase in £150m of annual restructuring costs. Nevertheless, full-year guidance was maintained.Standard Life slumped after the insurer said that its Chief Financial Officer Jackie Hunt is jumping ship and moving to sector peer Prudential to head up its UK and Europe division.Advertising and media firm WPP was out of favour early on after its first-quarter trading update. While the company said that its performance in the UK and emerging markets helped offset weaker growth in its mature markets in the US and Western Europe, it said that clients were still reluctant to take further risks in the face of challenging economic conditions.FTSE 100 - RisersCapita (CPI) 875.50p +1.51%Associated British Foods (ABF) 1,933.00p +0.99%Prudential (PRU) 1,100.00p +0.82%ITV (ITV) 128.30p +0.71%ARM Holdings (ARM) 995.00p +0.66%HSBC Holdings (HSBA) 694.80p +0.62%Reed Elsevier (REL) 780.50p +0.58%Imperial Tobacco Group (IMT) 2,300.00p +0.52%Unilever (ULVR) 2,773.00p +0.47%Sainsbury (J) (SBRY) 383.80p +0.47%FTSE 100 - FallersEurasian Natural Resources Corp. (ENRC) 278.60p -3.60%Evraz (EVR) 161.60p -3.00%Anglo American (AAL) 1,618.00p -1.88%Rio Tinto (RIO) 2,989.00p -1.74%Standard Life (SL.) 385.30p -1.68%Polymetal International (POLY) 774.00p -1.65%Antofagasta (ANTO) 940.00p -1.42%Vedanta Resources (VED) 1,211.00p -1.38%Petrofac Ltd. (PFC) 1,346.00p -1.32%Fresnillo (FRES) 1,154.00p -1.28%FTSE 250 - RisersNew World Resources A Shares (NWR) 156.90p +5.59%Rotork (ROR) 2,781.00p +3.00%Centamin (DI) (CEY) 44.74p +2.97%Drax Group (DRX) 616.00p +2.67%Spectris (SXS) 2,100.00p +2.14%Pennon Group (PNN) 682.50p +0.81%Merchants Trust (MRCH) 444.27p +0.74%Catlin Group Ltd. (CGL) 529.50p +0.67%Diploma (DPLM) 591.00p +0.60%Morgan Advance Materials (MGAM) 256.50p +0.59%FTSE 250 - FallersOcado Group (OCDO) 160.30p -4.64%Lonmin (LMI) 280.60p -3.64%Kazakhmys (KAZ) 362.50p -3.15%Filtrona PLC (FLTR) 696.50p -2.86%Fenner (FENR) 355.10p -2.28%Ferrexpo (FXPO) 179.60p -2.18%UBM (UBM) 705.50p -2.15%Genus (GNS) 1,375.00p -2.14%Fidessa Group (FDSA) 1,781.00p -1.87%Tullett Prebon (TLPR) 243.30p -1.78%BC