{"id":813803,"date":"2024-12-22T00:25:17","date_gmt":"2024-12-22T06:25:17","guid":{"rendered":"https:\/\/newsycanuse.com\/index.php\/2024\/12\/22\/rewriting-biology-textbooks-johns-hopkins-scientists-debunk-century-old-assumption-about-brain-cells\/"},"modified":"2024-12-22T00:25:17","modified_gmt":"2024-12-22T06:25:17","slug":"rewriting-biology-textbooks-johns-hopkins-scientists-debunk-century-old-assumption-about-brain-cells","status":"publish","type":"post","link":"https:\/\/newsycanuse.com\/index.php\/2024\/12\/22\/rewriting-biology-textbooks-johns-hopkins-scientists-debunk-century-old-assumption-about-brain-cells\/","title":{"rendered":"Rewriting Biology Textbooks: Johns Hopkins Scientists Debunk Century-Old Assumption About Brain Cells"},"content":{"rendered":"
\n
\"Neuron<\/a>
Axons in brain cells may resemble \u201cpearls on a string\u201d rather than tubes. A new study highlights how axon shape impacts brain signaling and offers new insights into neuron structure.<\/figcaption><\/figure>\n

Axons in brain cells resemble a string of pearls rather than smooth tubes, according to Johns Hopkins researchers. This discovery, aided by advanced imaging and modeling, reveals how physical and membrane properties influence axon structure and function, challenging long-held beliefs and offering insights into brain signaling and disease.<\/strong><\/p>\n

Biology textbooks may require revision, according to Johns Hopkins Medicine<\/a> scientists, who have presented new evidence suggesting that an armlike structure of mammalian brain cells might have a different shape than what scientists have assumed for over a century.<\/p>\n

Their study on mouse brain cells shows that the cells\u2019 axons \u2014 the armlike structures that reach out and exchange information with other brain cells \u2014 are not the cylindrical tubes often pictured in books and on websites but more like pearls on a string.<\/p>\n

A report on the findings was recently published in the journal Nature Neuroscience<\/em>.<\/p>\n

\u201cUnderstanding the structure of axons is important for understanding brain cell signaling,\u201d says Shigeki Watanabe, Ph.D., associate professor of cell biology and neuroscience at the Johns Hopkins University School of Medicine. \u201cAxons are the cables that connect our brain tissue, enabling learning, memory and other functions.\u201d<\/p>\n

Scientists have known that pearl-like structures in axons, referred to as axon beading, can develop in dying brain cells and in people with Parkinson\u2019s and other neurodegenerative diseases due to the loss of membrane and skeletal integrity in neurons.<\/p>\n

Under normal conditions, axons are thought to be shaped like tubes with a mostly constant diameter and occasional bubble-like structures (synaptic varicosities that hold globs of neurotransmitters, which enable signaling to other brain cells).<\/p>\n

Investigating Axon Pearling<\/h4>\n

Watanabe had initially seen repeated axon pearling in the nervous system of worms and grew more curious about the structures after a discussion with Swiss scientist Graham Knott, Ph.D. A research team from Harvard University had published a study in 2012<\/a> that identified repeated \u201cskeletal\u201d components in axons, so the pair of researchers discussed experiments to get rid of the axon skeleton to see if the pearl structures disappear, says Watanabe.<\/p>\n

Johns Hopkins graduate student and study first author Jacqueline Griswold tested the idea but found no effect on axon pearling.<\/p>\n

Then, Watanabe and Griswold worked with theoretical biophysics colleague Padmini Rangamani, Ph.D., professor of pharmacology at the University of California San Diego School of Medicine, to look more closely at axons\u2019 physical properties.<\/p>\n

\"Pearling<\/a>
Micrograph image of the \u201cpearling\u201d structure of an axon. Credit: Quan Gan, Mitsuo Suga, Shigeki Watanabe<\/figcaption><\/figure>\n

To be able to see axons on brain cells (neurons), which are 100 times smaller than the width of a human hair, the scientists used high pressure freezing electron microscopy. Like standard electron microscopy, which shoots beams of electrons at a cell to outline its structure, Watanabe and his team froze mouse neurons to preserve the structures\u2019 shape.<\/p>\n

\u201cTo see nanoscale<\/div>\n

The term "nanoscale" refers to dimensions that are measured in nanometers (nm), with one nanometer equaling one-billionth of a meter. This scale encompasses sizes from approximately 1 to 100 nanometers, where unique physical, chemical, and biological properties emerge that are not present in bulk materials. At the nanoscale, materials exhibit phenomena such as quantum effects and increased surface area to volume ratios, which can significantly alter their optical, electrical, and magnetic behaviors. These characteristics make nanoscale materials highly valuable for a wide range of applications, including electronics, medicine, and materials science.<\/div>\n

” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>nanoscale<\/span> structures with standard electron microscopy, we fix and dehydrate the tissues, but freezing them retains their shape \u2014 similar to freezing a grape rather than dehydrating it into a raisin,\u201d says Watanabe.<\/p>\n

The researchers studied three types of mouse neurons: ones grown in the lab, those taken from adult mice, and those taken from mouse embryos. The neurons were nonmyelinated (they were without the myelin-insulating cover that surrounds the axon).<\/p>\n

The researchers found the bubbly, pear shape of axons among all of the tens of thousands of images taken of the tissue samples.<\/p>\n

The scientists named the pearl-like structures in which the axon swells \u201cnon-synaptic varicosities.\u201d<\/p>\n

\u201cThese findings challenge a century of understanding about axon structure,\u201d says Watanabe.<\/p>\n

Insights from Mathematical Modeling and Experiments<\/h4>\n

The scientists also used mathematical modeling to see if the axon membrane influenced the shape or presence of the pearl on a string structure. They found that simple mechanical models could be used to explain these structures very effectively.<\/p>\n

Furthermore, experiments with the mathematical model and mouse brain samples showed that increasing the concentration of sugars in the solution around the axon or decreasing tension in the axonal membranes reduced the pearl structures\u2019 size.<\/p>\n

In another experiment, the scientists removed cholesterol from the neuron\u2019s membrane to make it less stiff and more fluid-like. Under this condition, they found less pearling in both mathematical models and mouse neurons, along with reduced ability of the axon to transmit electrical signals.<\/p>\n

\u201cA wider space in the axons allows ions [chemical particles] to pass through more quickly and avoid traffic jams,\u201d says Watanabe.<\/p>\n

The scientists also applied high frequency electrical stimulation to the mouse neurons, which made pearled structures along axons swell, on average, 8% longer and 17% wider for at least 30 min after stimulation and increased the speed of electrical signals. However, when cholesterol was removed from the membrane, the axon\u2019s pearls lost their swollen state and had no change in the speed of electrical signals.<\/p>\n

The research team plans to examine axonal \u201carms\u201d in human brain tissue taken with permission from people having brain surgery and those who have died from neurodegenerative diseases. This work formed the basis of a recently awarded Multiple Principal Investigator grant<\/a> to Watanabe and Rangamani<\/a> from the National Institute of Mental Health.<\/p>\n

Reference: \u201cMembrane mechanics dictate axonal pearls-on-a-string morphology and function\u201d by Jacqueline M. Griswold, Mayte Bonilla-Quintana, Renee Pepper, Christopher T. Lee, Sumana Raychaudhuri, Siyi Ma, Quan Gan, Sarah Syed, Cuncheng Zhu, Miriam Bell, Mitsuo Suga, Yuuki Yamaguchi, Ronan Ch\u00e9reau, U. Valentin N\u00e4gerl, Graham Knott, Padmini Rangamani and Shigeki Watanabe, 2 December 2024, Nature Neuroscience<\/i>.
\nDOI: 10.1038\/s41593-024-01813-1<\/a><\/p>\n

Funds for the research were provided by the Johns Hopkins University School of Medicine, the Marine Biological Laboratory Whitman Fellowship, the Chan Zuckerberg Initiative Collaborative Pair Grant and Supplement Award, the Brain Research Foundation Scientific Innovations Award, a Helis Foundation award, the National Institutes of Health<\/div>\n

The National Institutes of Health (NIH) is the primary agency of the United States government responsible for biomedical and public health research. Founded in 1887, it is a part of the U.S. Department of Health and Human Services. The NIH conducts its own scientific research through its Intramural Research Program (IRP) and provides major biomedical research funding to non-NIH research facilities through its Extramural Research Program. With 27 different institutes and centers under its umbrella, the NIH covers a broad spectrum of health-related research, including specific diseases, population health, clinical research, and fundamental biological processes. Its mission is to seek fundamental knowledge about the nature and behavior of living systems and the application of that knowledge to enhance health, lengthen life, and reduce illness and disability.<\/div>\n

” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>National Institutes of Health<\/span> (NS111133-01, NS105810-01A11, DA055668-01, 1RF1DA055668-01), the Air Force Office of Scientific Research (FA9550-18-1-0051), the Alfred P. Sloan Research Fellowship, a McKnight Foundation scholarship, a Klingenstein-Simons Fellowship Award in Neuroscience, a Vallee Foundation scholarship, the National Science Foundation and the Kavli Institutes at Johns Hopkins and UC San Diego.<\/p>\n

Other researchers who conducted the study are Chintan Patel, Renee Pepper, Sumana Raychaudhuri, Quan Gan, Sarah Syed and Brady Maher from Johns Hopkins, Mayte Bonilla-Quintana, Christopher Lee, Cuncheng Zhu and Miriam Bell from the UC San Diego, Siyi Ma from the Marine Biology Laboratory, Mitsuo Suga and Yuuki Yamaguchi from JEOL in Tokyo, and Ronan Ch\u00e9reau and U. Valentin N\u00e4gerl from the Universit\u00e9 de Bordeaux in France.<\/p>\n<\/p><\/div>\n

Johns Hopkins Medicine
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Axons in brain cells may resemble \u201cpearls on a string\u201d rather than tubes. A new study highlights how axon shape impacts brain signaling and offers new insights into neuron structure. Axons in brain cells resemble a string of pearls rather than smooth tubes, according to Johns Hopkins researchers. This discovery, aided by advanced imaging and<\/p>\n","protected":false},"author":1,"featured_media":813804,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24581,37573],"tags":[14526,110128],"class_list":{"0":"post-813803","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-biology","8":"category-rewriting","9":"tag-biology","10":"tag-rewriting"},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/newsycanuse.com\/index.php\/wp-json\/wp\/v2\/posts\/813803","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/newsycanuse.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/newsycanuse.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/newsycanuse.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/newsycanuse.com\/index.php\/wp-json\/wp\/v2\/comments?post=813803"}],"version-history":[{"count":0,"href":"https:\/\/newsycanuse.com\/index.php\/wp-json\/wp\/v2\/posts\/813803\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/newsycanuse.com\/index.php\/wp-json\/wp\/v2\/media\/813804"}],"wp:attachment":[{"href":"https:\/\/newsycanuse.com\/index.php\/wp-json\/wp\/v2\/media?parent=813803"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/newsycanuse.com\/index.php\/wp-json\/wp\/v2\/categories?post=813803"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/newsycanuse.com\/index.php\/wp-json\/wp\/v2\/tags?post=813803"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}