Why did you do this:
I have edit table wp_x_options:
siteurl: http://www.mydomain.com/news/
home: http://www.mydomain.com/news/
Domain mapping is for mapping domains, It is not for mapping domains and paths
table wp_domain_mapping:
domain: http://www.mydomain.com/news/
I'm not sure what you are trying to accomplish but given the complexity you might want to consider just make each site a separate WP install.