May 28, 1998

Article contends that police and school officials throughout country, in aftermath of recent string of school shootings by students in Oregon, Arkansas and Pennsylvania, are taking all youthful threats far more seriously, and in some cases, arresting youths who make them; officials say that they are not only concerned by potential violence but by possibility of copycat shooting by troubled student; recent examples cited (M)

Safety Warnings on Mir The top safety official for American astronauts says that NASA all but ignored his warnings that stays aboard the deteriorating Russian Mir space station were a ''disaster waiting to happen.'' Page A20. Nuclear Backlash in India Two weeks after India set off five nuclear tests, the Hindu nationalist-led Government encountered protests from lawmakers reflecting rising disquiet about the costs of acquiring nuclear weapons. Page A3.

Big Planet is using multilevel marketing scheme, in which independent salespeople are paid commissions based on sales of people they recruit, to offer everything from Internet access to paging and long-distance service, all consolidated in one monthly bill; Nu Skin USA, which sells cosmetics and nutritional supplements in similar way, owns majority interest in new venture; one discontinued Nu Skin unit allegedly charged representatives to sell nonexistent phone and other services; leading technology firms cited on Big Planet Web site as 'strategic partners' identify Big Planet only as customer; photos (M)

Russia mounts drastic effort to preserve value of its currency and stem exodus of foreign investors as its financial markets teeter on brink of collapse; officials triple interest rates, announce that they will be willing to accept lower price for selloff of Russia's last big oil company, Rosneft, and appeal for support from International Monetary Fund; Moscow's financial markets have been under siege as fears have mounted among investors and US officials that economic turmoil in Asia will spread to Russia; Moscow stock market is world's worst performing market, off more than 50 percent this year; swoon in market has turned into profound political crisis and has become major worry for US policymakers who have thrown their support behind Pres Boris N Yeltsin's Government; graph shows plunge in Russian stock market and rise in interest rates (M)

Clinton Administration tells state officials that it intends to require their Medicaid programs to pay for medically approved uses of impotence drug Viagra; says states can limit number of pills and prescriptions for drug; plans have upset state officials, who contend that decisions on coverage of Viagra should be left to states, which share Medicaid costs with Government; Pfizer Inc, maker of Viagra, suggests covering 10 pills a month if states insist on limit (M)