A judge on Tuesday granted an injunction that will keep some University of California hospital employees from participating in a planned strike at UC's five medical centers.

Sacramento County Superior Court Judge David Brown issued the injunction in response to a request made by the state labor board on the university's behalf. The injunction bars 49 workers whose jobs are considered critical to patient health and safety from taking part in the job action. That's about half the number UC wanted covered by an injunction, system spokeswoman Shelly Meron said.

Local 3299 of the American Federation of State, County and Municipal Employees has called for a one-day strike Wednesday at the university's hospitals in San Francisco, Los Angeles, Davis, Irvine and San Diego. The union represents 21,000 UC patient care and service employees, including radiation therapists who help treat cancer patients, MRI technicians, technicians who sterilize equipment used in surgeries, and pharmacy technicians who deliver medications to patients.

The union called the strike in response to what it said was intimidation by UC management of employees who participated in a two-day walkout in May. The May strike came after the union's contract expired and negotiations over a new pact failed.

The two sides are at odds over staffing, wages and benefits, including pensions and health care.

Todd Stenhouse, a spokesman for AFSCME Local 3299, said union officials had agreed before the injunction was issued to keep 50 critical care workers off the picket lines.

Stenhouse said the union has reduced its wage demands and made concessions on benefits but is holding the line on staffing demands that he said are needed for worker and patient safety.

Dwaine Duckett, UC vice president for systemwide human resources, urged the union in a letter to its leadership not to strike, saying that would hurt patients and drive the two sides further apart.

Some elective surgeries scheduled for Wednesday have been canceled, according to university officials. They say diagnoses and treatments may also be postponed because of delays in lab work and other tests.

Nurses were going to participate in Wednesday's strike in solidarity with the patient care workers, but then reached a tentative contract with UC in which they rescinded their planned participation.