LOS ANGELES (MarketWatch) -- A landmark measure to overhaul the nation's health-care system took a bite out of some insurers on Monday but didn't seem to hurt others in the industry, as the sector was generally up and helped push the broader equities market higher.

The NYSE Healthcare Index NYP.ID, +1.42% was up 40.55 points to 6,535.43.

Health-care companies in the S&P 500 at one point were the biggest gainers, and it was the only sector in the black early on, helping stocks climb in afternoon trading. S&P pharmaceuticals were the biggest gainers as they are expected to be a big winner in health-care reform.

Five of the nation's six biggest insurers traded down, reversing course after many started the day higher. Shares of two big Medicare beneficiaries -- HealthNet Inc. HNT and Humana Inc. HUM, +3.08% -- were down more than 1%, amid concerns of cuts in the government's insurance program for seniors. Meanwhile, UnitedHealth Group Inc. UNH, +2.50% , the nation's biggest insurer, lost 3.2%. WellPoint Inc. WLP was down 1%.

Cigna Inc. CI, +3.10% and Aetna Inc. AET, were the only gainers among the major firms, both up marginally.

Some minor insurers made bigger moves up, with Centene Corp. CNC, +4.42% leading the way. The company's shares were up more than 10.6% in the wake of a Friday announcement that the company's debt received an upgrade from Moody's Investors Service. But the company undoubtedly also benefited from its status as a Medicaid provider, and the expected increase in benefits for firms handling those accounts.

A ratings upgrade also helped Amerigroup Inc. AGP, +1.94% , shares of which moved up 4.3% after Barclays Capital raised its rating to buy from hold. And Molina Healthcare MOH, +6.54% climbed 4.5%.

In other sectors, hospital operator Health Management Associates HMA jumped 11.3% leading a rally for the hospital-nursing home sector. Tenet Healthcare Inc. THC, +4.34% was close behind, up more than 9%. A number of players in this sector made sizable gains, as hospitals may get the biggest relief from the health-care plan. The plan is geared to cut down on the uninsured, which should help hospitals' bottom line.

Also rising was Community Health Systems Inc. CYH, +1.93% , rallying 6.2%, and LifePoint Hospitals LPNT, jumping 5.8%.

Medical-device makers rose markedly as well, due mostly to favorable reviews from analysts as well as positive company news.

Shares of Medtronic Inc. MDT, +1.19% rose 2.3% after a clinical trial proved that a catheter-based fibrillation system proved more effective than anti-arrhythimia drugs.