EDMOND, Okla. -- North Dakota State remained the No. 1 team in the first regular-season NCAA Division II wrestling rankings of the 2001-02 eason on Wednesday, according to the NCAA Division II Wrestling Coaches' Association Top 20 poll.    The defending national champion Bison, who have captured three of the past four Division II national titles, received all eight first-place votes in a ballot of Division II coaches from around the country to finish with 160 points.    South Dakota State remained second in the poll, finishing with 146 points to edge out Central Oklahoma's 144-point total. Nebraska-Omaha was fourth with 139 points and Ashland (Ohio) fifth with 129 points in the balloting.    Rounding out the top 10 is Pittsburgh-Johnstown (Pa.), Western State (Colo.), Central Missouri State, Augustana (S.D.) and Minnesota State-Mankato.    NDSU has two top-ranked individuals in 174-pounder Todd Fuller and heavyweight Nick Severson, both defending national champions. Pittsburgh-Johnstown (149 Joe Lloyd and 157 Shad Benton) and Western State (141 Zac Stratton and 165 Dave Vondy) also have two top-ranked individuals each.