The persistence of unmetabolized 3H-7,12-dimethylbenz(a)anthracene in regenerating rat liver.

The hepatic subcellular distribution, binding and persistence of 3H-7,12-dimethylbenz(a)anthracene were compared in partially hepatectomized rats and in intact controls. By 2 weeks after injection, intact liver homogenates contained only 9% of the total radioactivity present 4 h after injection; regenerated liver contained 60% in spite of a tripling in liver mass during this time. Cell fractions isolated from regenerated liver had 9-59 fold greater hexane extractable specific activities than those from intact liver. The radioactivity present in hexane extracts co-chromatographed with a 3H-7,12-dimethylbenz(a)anthracene standard. Preliminary experiments demonstrated that liver microsomes isolated from DMBA treated partially hepatectomized animals metabolized less DMBA in vitro than did microsomes isolated from DMBA treated intact animals. The greater persistence of unmetabolized DMBA may be related to the greater carcinogenicity of this compound for regenerating, as compared with intact, rat liver

Clinical course and prognosis of trochlear nerve schwannomas

PURPOSE: To delineate the disease course and prognosis of patients with mass lesions of the fourth nerve presumed to be schwannomas. DESIGN: Nonrandomized retrospective case series. PARTICIPANTS: Thirty-seven consecutive cases of presumed trochlear nerve schwannoma from 9 tertiary university neuro-ophthalmology centers. METHODS: Cases were collected, and their clinical characteristics on presentation and follow-up are described. Inclusion criteria were brain magnetic resonance imaging (MRI) with a lesion suggestive of a schwannoma along the course of the fourth nerve. Exclusion criteria were other causes of fourth nerve palsy, such as congenital, traumatic or microvascular; normal (or lack of) initial brain MRI; lack of adequate clinical information; and disappearance of the lesion on subsequent follow-up brain MRI. MAIN OUTCOME MEASURES: Demographics of patients, presence of neurofibromatosis, symptoms on presentation, vertical deviation, lesion size (on presentation and follow-up), length of follow-up, and outcomes of treatment for lesions or diplopia. RESULTS: Seven patients were excluded and of the 30 patients included in our series, patients were predominantly male (77%) with a mean age of 51 years (range 9-102 years). In contrast with prior case reports, almost all of our cases had a fourth nerve palsy on presentation (29/30), often isolated. Mean follow-up was 3.1 years (range 0.2 months to 11.1 years). There was no significant difference between initial and follow-up lesion size (4.4 vs. 5 mm) for patients who did not receive treatment of lesions (P = 0.36). Only 3 patients underwent neurosurgical resection and an additional patient received gamma-knife radiotherapy. The majority of patients (24/30) did not pursue strabismus surgery for vertical diplopia. CONCLUSIONS: Patients with isolated fourth nerve palsy and small lesions of the fourth nerve have a good prognosis and should be followed with serial MRI scans without neurosurgical intervention unless they develop signs of brain stem compression. Most patients with diplopia and benign fourth nerve lesions typical of trochlear nerve schwannoma can adapt with either prism spectacles or no treatment at all, although strabismus surgery can be successful