Author Archives: Amy Proal

Disease-induced solitary confinement and the gut microbiome

November 25th, 2015 by Amy Proal
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What happens when a person dies alone, with no relatives or friends to provide information or help? Why do people die alone in some of the most populated areas of the world? A recent article in the New York Times delves into the topic by examining the life of George Bell, a man found dead in his Jackson Heights apartment in Queens, New York. I live just ten minutes away. His body was found after it had rotted to the point where neighbors noticed a smell. He knew only one person during the last decade of his life, a man he sometimes met at a bar. Yet with no family or friends in his life, it took over three months to identify his corpse.

I think that many readers may have started reading the article assuming that George Bell would, at the very least, have done some bad things to others. After all, before his death at 72, he spent nearly a decade living completely alone, with negligible social contact. How could that happen to an average, generally nice individual?

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Fungi in the Alzheimer’s brain and changing views on amyloid beta

November 18th, 2015 by Amy Proal
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Fungal species in different brain regions of patients with Alzheimers. (Soscia et al.)

Fungal species in different brain regions of patients with Alzheimers. (Pisa et al.)

Just a few days after writing my last post on microbes in the brain, I read a study that shows even more evidence of chronic infectious agents in brain tissue. In a paper published this month, Pisa and team at the Universidad Autónoma de Madrid studied the brains of patients with Alzheimer’s disease (AD). They found that all eleven AD brains studied were infected with a range of fungal organisms.

I am not surprised by the discovery. For one thing, inflammation of the central nervous system and immune activation play a major role in driving the Alzheimer’s disease process. Indeed, a number of cytokines, or immune system signaling molecules, are elevated in the brain of AD patients. This strongly suggests an activated immune response against pathogens. These cytokines include interleukins, tumor necrosis factor-α, and interferon-γ. Continue reading

The newly discovered lymphatic system in the brain, and a possible brain microbiome

November 11th, 2015 by Amy Proal
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The brain has long been considered to be a sterile organ, an “immunoprivileged” body site that microbes cannot directly enter and infect. Most medical textbooks still contend that microbes cannot enter the healthy brain due to a layer of endothelial cells that separate the brain from the body. This layer of cells, called the blood-brain barrier, is believed to separate circulating blood in the brain from fluid in the central nervous system and the rest of the body. Current dogma also dictates that bacteria are too large in shape and size to penetrate this barrier.

Despite this blood-brain “barrier”, researchers have regularly detected at least some pathogens in the brain: Borrelia, Group B streptococci, and Treponema pallidum – to name a just few. Such microbes’ presence is generally explained by the hypothesis that the blood-brain barrier becomes more permeable under conditions of inflammation. Certain pathogens, especially those able to survive inside of the cells of the immune system, are then considered capable of crossing into the brain’s circulatory system.

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Microbial signaling molecules drive cancer development

November 3rd, 2015 by Amy Proal
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For the past century, scientists have associated certain microbes or microbial populations with the development of cancer. A recent study by researchers at Ghent University in Belgium expands on this research by demonstrating a previously undiscovered mechanism by which gastrointestinal microbes can drive cancer processes. The study, Crosstalk between the microbiome and cancer cells by quorum sensing peptides shows how quorum sensing peptides synthesized by common gut bacteria can directly influence cancer cell growth and tumor formation.

Before proceeding, if you want to brush up on the concept of quorum sensing itself, watch this fascinating lecture by Princeton microbiologist Bonnie Bassler. If not, remember that quorum sensing peptides are produced by bacteria for purposes of communication with other microbes in their environment. Or that is their primary function. The above study shows that, at least in the laboratory, these peptides can additionally alter the expression of human genes.

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