The parent company of North Adams Regional Hospital filed for Chapter 11 bankruptcy protection on Monday in U.S. Bankruptcy Court in Springfield. Northern Berkshire Healthcare officials say the move is necessary: Six months of intense negotiations with bondholders hasn't yielded an agreement that would restructure and permanently reduce the organization's $43 million in bond debt. NBH's overall debt, which includes capital leases and mortgages, is $49.5 million. Much of the $43 million in bond debt is related to the expansion of North Adams Regional Hospital and the remaining debt associated with the purchase of the Sweet Brook nursing home and the Sweetwood assisted living facility in 1999. Board of Trustees Chairman Dr. Arthur Turton said Chapter 11 will allow the organization to restructure its debt to a more manageable size and emerge from bankruptcy protection proceedings with a more fiscally.