Evaluation of Copper Chelation Therapy in a Transgenic Rat Model of Cerebral Amyloid Angiopathy.

Cerebral amyloid angiopathy (CAA) is characterized by the accumulation of the amyloid ß (Aß) protein in blood vessels and leads to hemorrhages, strokes, and dementia in elderly individuals. Recent reports have shown elevated copper levels colocalized with vascular amyloid in human CAA and Alzheimer's disease patients, which have been suggested to contribute to cytotoxicity through the formation of reactive oxygen species. Here, we treated a transgenic rat model of CAA (rTg-DI) with the copper-specific chelator, tetrathiomolybdate (TTM), via intraperitoneal (IP) administration for 6 months to determine if it could lower copper content in vascular amyloid deposits and modify CAA pathology. Results showed that TTM treatment led to elevated Aß load in the hippocampus of the rTg-DI rats and increased microbleeds in the wild type (WT) animals. X-ray fluorescence microscopy was performed to image the distribution of copper and revealed a surprising increase in copper colocalized with Aß aggregates in TTM-treated rTg-DI rats. Unexpectedly, we also found an increase in the copper content in unaffected vessels of both rTg-DI and WT animals. These results show that IP administration of TTM was ineffective in removing copper from vascular Aß aggregates in vivo and increased the development of disease pathology in CAA.

Reducing Frost during Cryoimaging Using a Hygroscopic Ice Frame.

Cryomicroscopy is commonly hampered by frost accumulation, reducing the visual clarity of the specimen. Pulling a vacuum or purging with nitrogen gas can greatly reduce the sample chamber's humidity, but at cryogenic temperatures, even minute concentrations of water vapor can still result in frost deposition. Here, a hygroscopic ice frame was created around the specimen to suppress frost growth during cryomicroscopy. Specifically, fluorescently tagged rat brain vessels were frozen on a silicon nitride window with an ice frame, and the luminescence of the fluorescent tag was improved by a factor of 6 compared to a similar specimen in only a nitrogen purge environment. These findings suggest that the simple implementation of a hygroscopic ice frame surrounding the specimen can substantially improve the visual clarity for cryomicroscopy, beyond that of a vacuum or nitrogen purge system.