NEW HAVEN, CONN. — The United States Patent Office issued 99,275 patents in 1990, according to MicroPatent, which publishes patent information on compact disks. The total is 3 percent lower than 1989, but nearly 20 percent above the total for any previous year. American inventors were granted 53 percent of the patents, compared to 61 percent 10 years ago. Only eight US companies were among the top 20 in terms of number of patents issued to them. The top five were all Japanese firms. -PATHNAME- /usr/local/etc/httpd/plweb/DBGROUPS/paper/database/tape/91/mar/week10/firm.