In the second-quarter financial results that the nation’s largest banks have announced over the last two weeks, revenue has dropped across several business lines, pressured by the continuing economic malaise. But the pain in the fixed-income operations — called that because of the fixed interest rate that most bonds pay — has been particularly acute.

Morgan Stanley’s second-quarter fixed-income sales and trading revenue declined 60 percent from the previous year, more than other parts of its operations. Companywide, the bank said that it would be cutting about 7 percent of its work force this year. No banks report the specific staffing levels of their bond operations.

Fixed-income desks help companies and government agencies raise money by selling bonds to the public. They have made even more money trading existing bonds for their own account and on behalf of clients such as pensions and mutual funds, and managing the portfolios of these clients. The same divisions at banks have also bought and sold derivatives, financial contracts whose prices are based on bond values.

But those derivatives are being forced onto open exchanges or other platforms under the Dodd-Frank financial regulation law. Other new rules, requiring strong capital buffers, have made it more expensive for banks to hold the large inventories of bonds that allow them to serve as the middleman for buyers and sellers. Money managers and banks are creating open electronic marketplaces for trading government and corporate bonds. Still more new rules will limit banks from using their own money to make financial bets on bonds.

The series of changes will make it easier for regulators to monitor these complex markets and could drive down the large cut that banks take from most bond trades and make it cheaper for investors to buy and sell bonds. But some industry experts have said that more transparency in the trading of bonds could make it harder to buy and sell some less popular bonds because investors will not want to have their enormous trades exposed. This could drive up the cost of borrowing for companies and governments.