Research Report: Why don’t we all get Alzheimer’s disease?


By Lynne Friedmann

Every human brain contains the ingredients necessary to spark Alzheimer’s disease (AD). But while an estimated 5 million Americans have AD, the vast majority of people do not (and will not) develop the devastating neurological condition.

How is that possible? Researchers from UC San Diego School of Medicine have uncovered a “trick of nature” that maintains critical separation between a protein and an enzyme that, when combined, triggers the progressive cell degeneration and death characteristic of AD.

Most neuroscientists believe AD is caused by accumulating assemblies of beta-amyloid protein (“plaques”) that trigger a sequence of events that leads to impaired cell function and death. Creating beta-amyloid requires the convergence of a protein called amyloid precursor protein (APP) and an enzyme that cleaves APP into smaller toxic fragments called beta-secretase or BACE-1.

Using cultured hippocampal neurons and tissue from human and mouse brains, researchers discovered that healthy brain cells largely segregate APP and BACE-1 into distinct compartments as soon as they are manufactured, ensuring the two proteins do not have much contact with each other.

— Findings appear in the journal


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• Oxygen increase led to evolution explosion

A team that includes researchers from Scripps Institution of Oceanography at UC San Diego has linked increasing oxygen levels and the rise and evolution of carnivores as the force behind a broad explosion 500- to 540-million years ago of species and body-structure adaptations that resulted in the animal diversity seen today.

Although the cause of the influx of oxygen remains a matter a scientific controversy, the “Cambrian radiation” that followed was the most significant evolutionary event in the history of animals during which essentially every major animal body plan — from arthropods to mollusks to chordates, the phylum to which humans belong — appeared in the fossil record.

The authors linked this proliferation of life to the evolution of the carnivorous mode of feeding, which requires higher oxygen concentrations. Thus, once oxygen increased, animals started consuming other animals, stimulating the Cambrian radiation through an escalating predator-prey “arms race.”

This study suggests the reverse may occur — with limitations on the abundance and types of carnivore species — as low-oxygen zones (so-called dead zones) continue to appear and expand. Thus, understanding past evolutionary events may help researchers recognize and manage the effects of ocean oxygen zones in modern oceans.

— The study appears in the

Proceedings of the National Academy of Sciences

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• Cleaning solar panels not worth the cost

Researchers from the Jacobs School of Engineering at UC San Diego found that solar panels not cleaned, or rained on, for 145 days during a summer drought in California, lost only 7.4 percent of their efficiency. Overall, for a typical residential solar system of 5 kilowatts, washing panels halfway through the summer would translate into a mere $20 gain in electricity production. For larger commercial rooftop systems, the financial losses are bigger but still rarely enough to warrant the cost of washing the panels.

Researchers analyzed data from the California Solar Initiative showing solar panel output at 186 residential and commercial sites from the San Francisco Bay area to the United States-Mexico border in 2010. They compared output after more than 0.1 inches of rain fell on the panels with output during the summer drought California experienced that year.

Survey findings are widely applicable because pollution and dust levels in California are fairly representative of the rest of the United States — and possibly higher. If anything, other areas of the country get more rain, resulting in cleaner panels and even smaller efficiency losses.

— Findings appear in the journal

Solar Energy

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Simple math brings new understanding to biological process

One of the most basic and intensively studied processes in biology has gained a new level of understanding, thanks to the application of simple math to a problem that scientists never thought could benefit from mathematics.

UCSD physicists and biologists found that the process bacteria use to quickly adapt to metabolize preferred energy sources such as glucose — a process called “catabolite repression”— is controlled not just by glucose, as had long been accepted, but just as much by other essential nutrients, such as nitrogen and sulfur.

The surprising finding was arrived at by a new approach called “quantitative biology,” in which scientists quantify biological data and discover mathematical patterns, which in turn guide them to develop predictive models of underlying processes. This mode of research — data quantitation and model building — has driven the progress of physics for the past several centuries.

Significance of the study is that it demonstrates that the physicists’ quantitative approach can effectively probe and explain biological processes, even a classic problem that has been heavily scrutinized.

— Findings appear in the journal


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Lynne Friedmann is a science writer based in Solana Beach.