The S&P/ASX 200 (Index: ^AJXO) (ASX: XJO) has opened higher this morning supported by the latest opinion polls in the UK that suggest the people of Britain may vote to remain within the European Union. However, the vote remains on a knife edge and this week will be volatile for the local share market.

Below are four shares performing especially well today, so let’s take a look at what may be behind their strong start to the week.

Henderson Group plc (ASX: HGG) is the UK-based fund manager with leverage to European equity markets and the strength of the UK pound. The shares are up 4.3% to $5.04 today on renewed expectations that Britain will stay within the EU. Investors can expect a big swing in the stock’s price on Friday June 24 depending on the result of the EU referendum.

CYBG PLC CDI 1:1 (ASX: CYB) the UK bank more commonly known as Clydesdale and Yorkshire Bank is up 5.8% to $5.51 in morning trade also on renewed expectations that Britain will vote to remain in the EU. Formerly owned by the NAB the Clydesdale Bank recently reported a half-year profit of GBP 107 million, although it retains a mixed outlook in a competitive UK banking environment.

Santos Ltd (ASX: STO) shares are up 5.6% to $4.53 this morning as the oil price surged more than 4% over the weekend to nudge the $US50 per barrel level. The company is heavily indebted after investing in its Gladstone LNG project, which is now moving towards full capacity estimated to be up to 7.8 million tonnes of LNG production per year. The company’s fortunes remain tied to energy prices with shares likely to remain volatile given the debt to equity profile means this company carries more risk than its mid to large-cap energy peers.

Mesoblast limited (ASX: MSB) shares are up 10% to $1.17 in morning trade despite the company releasing no news since updating the market that a business partner had walked away from a key commercial agreement. The company posted a cash outflow of US$22 million for the quarter ending March 31 2016 with around US$100 million in cash on its balance sheet. It now needs to find additional funds to complete its clinical trials for chronic heart failure and has little in the way of revenues. Given the rapid cash burn and recent loss of a funding partner, I expect the share price could resume its move downwards over the week.

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Motley Fool contributor Tom Richardson has no position in any stocks mentioned.

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The Motley Fool Australia has no position in any of the stocks mentioned. 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. This article contains general investment advice only (under AFSL 400691). Authorised by Bruce Jackson.