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While transgenic mice have great promise in the study of Alzheimer's disease (AD), uncertainties remain about the extent to which they provide a model of the disorder or the best way to characterize disease progression. Using fluorodeoxyglucose (FDG) autoradiography, we found that transgenic mice over-expressing a mutant form of the human amyloid precursor protein have preferentially and progressively reduced activity in the posterior cingulate cortex and relatively spared activity in visual cortex, sensorimotor cortex, cerebellum and brain stem, a pattern previously demonstrated in FDG PET studies of persons with Alzheimer's disease, Brain imaging of posterior cingulate activity could provide an indicator of AD in suitable animals, helping to clarify disease mechanisms and screen candidate treatments.

Deficits in oxidative phosphorylation have been implicated in many neurodegenerative diseases. In this study, cytochrome oxidase activity was inhibited following a 28-d systemic administration of nonlethal sodium azide via subcutaneous osmotic pumps. Quantitative enzyme histochemistry was performed on tissue sections from brain, skeletal muscle, and heart to localize cytochrome oxidase activity both globally and in regions within each tissue. Significant decreases of cytochrome oxidase activity were found in the brain and skeletal muscle but not heart. In addition, regions within each tissue were also analyzed, such as cortex and striatum in the brain and red and white fibers in skeletal muscle. The tissue specific inhibition of cytochrome oxidase by sodium azide could serve as a positive control for studies of other mitochondrial toxins in aerobically compromised cells. Therefore, chronic nonlethal sodium azide administration may provide a potential rat model for the study of mitochondrial dysfunction and the role of environmental pollutants in brain and muscle tissues affected in certain neurodegenerative diseases.

Otoacoustic emissions (OAEs) were monitored in two human males undergoing estrogen treatment prior to sex-reversal surgery. In one subject, multiple spontaneous emissions (SOAEs) appeared where none had been evident previously. One reasonable interpretation is that (in this male, at least) androgens normally produced a suppressive effect on the cochlear mechanisms responsible for SOAEs, and that the decline in androgen levels produced by the estrogenic drug led to a reduction in that suppression.