Today marked Day Two of a walk-out by TAs at the University of Wisconsin: Members of the Teaching Assistants' Association, which has a campus membership of 1,900, walked picket lines at university buildings protesting pay and benefits issues following unsuccessful negotiations with the State Employment Relations Office, which handles labor contract talks for the State of Wisconsin. The primary point of contention is the state's insistence that teaching assistants begin to pay some of their health-insurance costs. Union officials say the assistants' pay averages about $10,000 for nine months' work. Under the proposed state plan, an unmarried graduate student would contribute about $9 a month toward health-care costs, university officials say. Union officials say they would make the contribution if their salaries were raised to levels matching that of graduate students at comparable universities.