 Shares of Union Pacific Corp. UNP, 0.70 shed 1.0 in premarket trading Tuesday, after the railroad operator reported fourth-quarter profit and revenue that came up shy of Wall Street expectations, as continued challenges in hiring, inflation and extreme winter weather were weighed against growth in carloads. Net income fell to 1.64 billion, or 2.67 a share, from 1.71 billion, or 2.66 a share, in the year-ago period, as the number of shares outstanding was reduced by 4.4. 