Unemployment in Lake and Mendocino counties was up slightly in December. Professional and business services posted the most month-over-month job losses, the state agency reported. Mendocino County’s rate was 5.4%, up from 4.8% in November and up more than a point over last year’s 4.3%. Lake County’s unemployment rate was higher, at 6.9%, up from a revised 6.1% in November. The rate for the same time last year was 5.4%.