Point mutations within the beta-amyloid precusor protein (beta-APP) gene known to segregate with Alzheimer's disease in certain families were introduced into human beta-APP cDNAs and expressed under the control of a neuron-specific enolase (NSE) promoter in mice. The transgenic animals exhibited transgene expression predominantly in neocortex and hippocampus where the levels were maximally 1.3-fold of those of wild-type mouse beta-APP. Quantitative immunoblot analysis in homozygous mice carrying different missense mutations showed slightly increased alpha-secretory processing. In V7171 mice compared to nontransgenic mice there was more alpha-secretory beta-APP (beta-APPsec) in cortex/hippocampus, less in cerebellum, and no difference in midbrain/brain stem. In none of the transgenic animals tested was a 4 kDa amyloid fragment detected by Western blotting of brain extracts, immunohistochemistry, or by 125I-A beta-binding onto brain sections. No glial reaction was observed. Behavioral analysis of mice carrying the V7171 mutation showed no appreciable deficit in comparison to wild-type mice. Together, these data suggest that low levels of expression of mutated beta-APP in 10-12-month-old transgenic mouse brains result in slightly more beta-APPsec, and are insufficient to induce amyloidogenic processing and AD-like pathology.

Alzheimer Disease↗

PubMedDate not supplied

Short-term CT and MR changes in brain tumors following 125I interstitial irradiation.

PURPOSE: The study was undertaken to assess characteristic short-term CT and MR changes in brain tumors following 125I interstitial irradiation. METHOD: Sixteen patients were included who had both CT and MR control examinations at regular intervals over a period of 18 months following treatment. Two groups were distinguished: low grade tumors (11 cases) and high grade malignancies (5 patients). 125I seeds were used as temporary implants. The cumulative dose was 50-60 Gy. RESULTS: In some patients of both groups, a low attenuation spheric structure with a contrast-medium-enhanced ring and a diameter of 6-8 mm was observed. There was no edema around the structure, which represents a zone of tissue necrosis at the site of the temporary 125I implant. Tumors in both groups were completely destroyed, some decreased in size, and others were unchanged. Pseudotumor necrosis with accompanying edema occurred in two patients with low grade astrocytoma, the diameter of which was > 4 cm. CONCLUSION: The behavior of cerebral tumors and their appearance on CT and MR images after interstitial irradiation seem to be variable. Decrease in tumor size may take place at different intervals after therapy. Brachytherapy of tumors with a diameter of > 4 cm may produce space-occupying radionecrosis.

Adult↗