{"id":132701,"date":"2024-12-03T03:57:17","date_gmt":"2024-12-02T20:57:17","guid":{"rendered":"https:\/\/hotvideos24.online\/?p=132701"},"modified":"2024-12-03T03:57:17","modified_gmt":"2024-12-02T20:57:17","slug":"study-reveals-axons-are-like-pearls-on-a-string","status":"publish","type":"post","link":"https:\/\/hotvideos24.online\/?p=132701","title":{"rendered":"Study Reveals Axons Are Like &#8220;Pearls on a String&#8221;"},"content":{"rendered":"<p> <script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-3711241968723425\"\r\n     crossorigin=\"anonymous\"><\/script>\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:block\"\r\n     data-ad-format=\"fluid\"\r\n     data-ad-layout-key=\"-fb+5w+4e-db+86\"\r\n     data-ad-client=\"ca-pub-3711241968723425\"\r\n     data-ad-slot=\"7910942971\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><br \/>\n<\/p>\n<div>\n<p><strong>Summary: <\/strong>A new study challenges the long-held belief that axons, brain cell extensions, are tube-like, revealing instead a \u201cpearl-on-a-string\u201d structure.<\/p>\n<p>Using advanced freezing electron microscopy, researchers found these bead-like formations, termed \u201cnon-synaptic varicosities,\u201d across mouse neurons. These structures may influence brain signaling by modulating ion flow and electrical signal speed. Changes in membrane stiffness, such as reduced cholesterol levels, alter the pearls\u2019 size and signal transmission ability.<\/p>\n<p>This discovery reshapes our understanding of neuron structure and opens doors for exploring its implications in neurodegenerative diseases. Future work will examine these formations in human brain tissues.<\/p>\n<p><strong>Key Facts:<\/strong><\/p>\n<ul class=\"wp-block-list\">\n<li>Axons exhibit \u201cpearl-on-a-string\u201d shapes, not constant cylindrical tubes.<\/li>\n<li>Removing cholesterol in axons reduces pearling and slows electrical signals.<\/li>\n<li>High-frequency electrical stimulation temporarily swells these pearl structures.<\/li>\n<\/ul>\n<p><strong>Source: <\/strong>Johns Hopkins Medicine<\/p>\n<p><strong>Biology textbooks may need a revision, say Johns Hopkins Medicine scientists, who present new evidence that an armlike structure of mammalian brain cells may be a different shape than scientists have assumed for more than a century.<\/strong>\u00a0<\/p>\n<p>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.\u00a0<\/p>\n<figure class=\"wp-block-image size-full\"><picture fetchpriority=\"high\" decoding=\"async\" class=\"wp-image-106625\"><source type=\"image\/webp\" srcset=\"https:\/\/neurosciencenews.com\/files\/2024\/12\/axon-shape-neuroscience.jpg.webp 1200w, https:\/\/neurosciencenews.com\/files\/2024\/12\/axon-shape-neuroscience-300x160.jpg.webp 300w, https:\/\/neurosciencenews.com\/files\/2024\/12\/axon-shape-neuroscience-770x410.jpg.webp 770w, https:\/\/neurosciencenews.com\/files\/2024\/12\/axon-shape-neuroscience-293x156.jpg.webp 293w, https:\/\/neurosciencenews.com\/files\/2024\/12\/axon-shape-neuroscience-150x80.jpg.webp 150w\" sizes=\"(max-width: 1200px) 100vw, 1200px\"\/><img fetchpriority=\"high\" decoding=\"async\" width=\"1200\" height=\"639\" src=\"https:\/\/neurosciencenews.com\/files\/2024\/12\/axon-shape-neuroscience.jpg\" alt=\"This shows axons.\" srcset=\"https:\/\/neurosciencenews.com\/files\/2024\/12\/axon-shape-neuroscience.jpg 1200w, https:\/\/neurosciencenews.com\/files\/2024\/12\/axon-shape-neuroscience-300x160.jpg 300w, https:\/\/neurosciencenews.com\/files\/2024\/12\/axon-shape-neuroscience-770x410.jpg 770w, https:\/\/neurosciencenews.com\/files\/2024\/12\/axon-shape-neuroscience-293x156.jpg 293w, https:\/\/neurosciencenews.com\/files\/2024\/12\/axon-shape-neuroscience-150x80.jpg 150w\" sizes=\"(max-width: 1200px) 100vw, 1200px\"\/> <\/picture><figcaption class=\"wp-element-caption\">Micrograph image of the \u201cpearling\u201d structure of an axon. Credit: Quan Gan, Mitsuo Suga, Shigeki Watanabe<\/figcaption><\/figure>\n<p>A report on the findings\u00a0is published online Dec. 2 in\u00a0<em>Nature Neuroscience<\/em>.\u00a0<\/p>\n<p>\u201cUnderstanding the structure of axons is important for understanding brain cell signaling,\u201d says\u00a0Shigeki 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\u00a0<\/p>\n<p>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.\u00a0<\/p>\n<p>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).\u00a0<\/p>\n<p>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\u00a0a study in 2012\u00a0that 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.\u00a0<\/p>\n<p>Johns Hopkins graduate student and study first author Jacqueline Griswold tested the idea but found no effect on axon pearling.\u00a0<\/p>\n<p>Then, Watanabe and Griswold worked with theoretical biophysics colleague\u00a0Padmini Rangamani, Ph.D., professor of pharmacology at University of California San Diego School of Medicine, to look more closely at axons\u2019 physical properties.\u00a0<\/p>\n<p>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.<\/p>\n<p>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.\u00a0<\/p>\n<p>\u201cTo see nanoscale 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.\u00a0<\/p>\n<p>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).\u00a0<\/p>\n<p>The researchers found the bubbly, pear shape of axons among all of the tens of thousands of images taken of the tissue samples.\u00a0<\/p>\n<p>The scientists named the pearl-like structures in which the axon swells \u201cnon-synaptic varicosities.\u201d\u00a0<\/p>\n<p>\u201cThese findings challenge a century of understanding about axon structure,\u201d says Watanabe.\u00a0<\/p>\n<p>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.\u00a0<\/p>\n<p>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.\u00a0<\/p>\n<p>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.\u00a0<\/p>\n<p>\u201cA wider space in the axons allows ions [chemical particles] to pass through more quickly and avoid traffic jams,\u201d says Watanabe.\u00a0<\/p>\n<p>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.<\/p>\n<p>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.\u00a0<\/p>\n<p>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.<\/p>\n<p>This work formed the basis of a recently awarded\u00a0Multiple Principal Investigator grant\u00a0to\u00a0Watanabe and Rangamani\u00a0from the National Institute of Mental Health.\u00a0<\/p>\n<p><strong>Funding: <\/strong>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 (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.\u00a0<\/p>\n<p>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.\u00a0<\/p>\n<h2 class=\"wp-block-heading\">About this neuroscience research news<\/h2>\n<p class=\"has-background\" style=\"background-color:#ffffe8\"><strong>Author: <\/strong><a href=\"http:\/\/neurosciencenews.com\/cdn-cgi\/l\/email-protection#acdbcddfd8cdecc6c4c1c582c9c8d9\" target=\"_blank\" rel=\"noreferrer noopener\">Vanessa Wasta<\/a><br \/><strong>Source: <\/strong><a href=\"https:\/\/jhmi.edu\" target=\"_blank\" rel=\"noreferrer noopener\">Johns Hopkins Medicine<\/a><br \/><strong>Contact: <\/strong>Vanessa Wasta \u2013 Johns Hopkins Medicine<br \/><strong>Image: <\/strong>The image is credited to Quan Gan, Mitsuo Suga, Shigeki Watanabe<\/p>\n<p class=\"has-background\" style=\"background-color:#ffffe8\"><strong>Original Research: <\/strong>Open access.<br \/>\u201c<a href=\"https:\/\/doi.org\/10.1038\/s41593-024-01813-1\" target=\"_blank\" rel=\"noreferrer noopener\">Membrane mechanics dictate axonal pearls-on-a-string morphology and function<\/a>\u201d by Shigeki Watanabe et al. <em>Nature Neuroscience<\/em><\/p>\n<hr class=\"wp-block-separator has-text-color has-pale-cyan-blue-color has-alpha-channel-opacity has-pale-cyan-blue-background-color has-background\"\/>\n<p><strong>Abstract<\/strong><\/p>\n<p><strong>Membrane mechanics dictate axonal pearls-on-a-string morphology and function<\/strong><\/p>\n<p>Axons are ultrathin membrane cables that are specialized for the conduction of action potentials. Although their diameter is variable along their length, how their morphology is determined is unclear.<\/p>\n<p>Here, we demonstrate that unmyelinated axons of the mouse central nervous system have nonsynaptic, nanoscopic varicosities ~200\u2009nm in diameter repeatedly along their length interspersed with a thin cable ~60\u2009nm in diameter like pearls-on-a-string. In silico modeling suggests that this axon nanopearling can be explained by membrane mechanical properties.<\/p>\n<p>Treatments disrupting membrane properties, such as hyper- or hypotonic solutions, cholesterol removal and nonmuscle myosin II inhibition, alter axon nanopearling, confirming the role of membrane mechanics in determining axon morphology.<\/p>\n<p>Furthermore, neuronal activity modulates plasma membrane cholesterol concentration, leading to changes in axon nanopearls and causing slowing of action potential conduction velocity.<\/p>\n<p>These data reveal that biophysical forces dictate axon morphology and function, and modulation of membrane mechanics likely underlies unmyelinated axonal plasticity.<\/p>\n<p> <!-- Form created by Optin Forms plugin by WPKube: create beautiful optin forms with ease! --> <!-- https:\/\/wpkube.com\/ --><!--optinforms-form5-container--> <!-- \/ Optin Forms --> <\/div>\n<p><script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-3711241968723425\"\r\n     crossorigin=\"anonymous\"><\/script>\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:block\"\r\n     data-ad-format=\"fluid\"\r\n     data-ad-layout-key=\"-fb+5w+4e-db+86\"\r\n     data-ad-client=\"ca-pub-3711241968723425\"\r\n     data-ad-slot=\"7910942971\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><br \/>\n<br \/><div data-type=\"_mgwidget\" data-widget-id=\"1660802\">\r\n<\/div>\r\n<script>(function(w,q){w[q]=w[q]||[];w[q].push([\"_mgc.load\"])})(window,\"_mgq\");\r\n<\/script>\r\n<br \/>\n<br \/><a href=\"https:\/\/neurosciencenews.com\/axons-pearl-shape-neuroscience-28151\/\">Source link <\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Summary: A new study challenges the long-held belief that axons, brain cell extensions, are tube-like, revealing instead a \u201cpearl-on-a-string\u201d structure. Using advanced freezing electron microscopy, researchers found these bead-like formations, &hellip; <a href=\"https:\/\/hotvideos24.online\/?p=132701\" class=\"more-link\">Read More<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8628],"tags":[],"class_list":["post-132701","post","type-post","status-publish","format-standard","hentry","category-science","entry"],"_links":{"self":[{"href":"https:\/\/hotvideos24.online\/index.php?rest_route=\/wp\/v2\/posts\/132701","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/hotvideos24.online\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hotvideos24.online\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hotvideos24.online\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/hotvideos24.online\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=132701"}],"version-history":[{"count":0,"href":"https:\/\/hotvideos24.online\/index.php?rest_route=\/wp\/v2\/posts\/132701\/revisions"}],"wp:attachment":[{"href":"https:\/\/hotvideos24.online\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=132701"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hotvideos24.online\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=132701"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hotvideos24.online\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=132701"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}