LONDON -- The FTSE 100 (FTSEINDICES:^FTSE) is picking up today after a gloomy four days of straight losses. After closing on 6,416 points last Thursday, the index of top U.K. shares slid to a close yesterday of 6,244. Today it's up 0.33% to 6,265 as of 8:35 a.m. EDT, but general sentiment still seems bearish -- there's downward pressure on commodity-related shares, with some commentators even predicting a slide back to 6,000.

But which individual shares are underperforming the index today? Here are three that are looking a bit shaky.

Barclays (LSE:BARC) (NYSE:BCS)
Barclays shares have dipped 0.6% to 289 pence this morning after the high-street bank announced that its investment-banking head, Rich Ricci, is leaving. There had been much speculation that his days were numbered since the arrival of new chief executive Antony Jenkins.

And in a further management shakeup, the bank's head of wealth management, Tom Kalaris, is to retire -- bringing to an end the era of top managers who were close to ex-boss Bob Diamond.

The Weir Group price has dipped 0.4% to 2,127 pence after the engineer extended its presence in the mining and minerals business with a new deal with German firm KHD. Weir has acted as KHD's exclusive agent since 2010, and the new agreement will see Weir taking "direct control over the design, manufacture and distribution of High Pressure Grinding Rolls in minerals processing applications using KHD technology."

On the face of it, it looks like a good move, but maybe bearish sentiment toward commodities is behind the share price fall.

Monitise (LSE:MONI)
In another case of apparently positive news presaging a price fall, shares in Monitise have dipped 0.7% to 34 pence this morning on the announcement of "two additions to Visa Europe's Personal Payments mobile service it has helped develop."

A new Multi-Currency facility later in the year should significantly ease international payments, while the Immediate Payments system, launching this week, will allow personal payments to be completed in minutes.

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Alan Oscroft has no position in any stocks mentioned. The Motley Fool recommends Weir Group. The Motley Fool owns shares of Monitise. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.