Investec kept a 'hold' stance on oil major BP, but said that the company's first-quarter trading update showed a 'solid start to the year'."We do not expect any major changes to either our forecasts or consensus. BP is trading broadly in line with the sector which, given current Russian risk, looks about right," Investec said.Panmure Gordon has upgraded its recommendation for AstraZeneca from 'hold' to 'buy', saying that a potential takeover by US pharmaceutical peer Pfizer is likely.Panmure said that a bid of 5,300-5,400p a share "may tempt AstraZeneca shareholders", compared with the tentative 4,661p-a-share approach that was rejected.Cantor Fitzgerald has said that another profit warning from Serco is "highly concerning" and believes that the road to recovery is likely to be a long one for the outsourcing group."We have expressed our concern in recent research notes over the reputational impact of Serco's government woes. Yesterday's statement seems to vindicate our view and suggests that Serco's problems are more deeply rooted than previously expected," said Cantor Analyst Caroline de La Soujeole.Numis Securities has maintained a 'buy' rating for Telecity after a strong first-quarter trading update from the Europe-focused data centre provider on Tuesday.The broker, which left its target price of 880p unchanged, said that the stock's valuations "don't look at all expensive if we can see a return to good levels of growth and high certainty in forecasts".BC