Myelin and its Prevalence in the Nervous System by Patrick Castillo

Nodes of Ranvier

castillo219 — 2022-04-04 18:50:40 UTC

The nodes of Ranvier are specialized regions on the axon that are not covered by myelin¹. Even though this segment of the axon is not insulated with myelin, the rest of the axon is insulated to allow for signal conduction to travel faster. These nodes contain high concentrations of sodium-gated ion channels, which help in the fast conduction of action potentials. It is French histologist Louis-Antoine Ranvier who discovered these structures in 1878².

the image above shows the anatomy of a basic neuron and the indication of a Node of Ranvier³.

Sources:

1) Grider MH, Belcea CQ, Covington BP, et al. Neuroanatomy, Nodes of Ranvier. [Updated 2021 Jul 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537273/

2) Node of Ranvier | anatomy. (2016). Encyclopedia Britannica. https://www.britannica.com/science/node-of-Ranvier

3) https://study.com/cimages/videopreview/nodes-of-ranvier-function-and-definition_01003612_139998.jpg

Who is my Docent?

castillo219 — 2022-04-04 18:52:33 UTC

Robert Remak would be the perfect docent for this exhibit. This is because of his extensive knowledge and works dedicated to myelin research and his famous discovery of nuclei in unmyelinated organic axon fibers². Remak was a German scientist from Posen, Prussia¹. Remak had a very extensive background in neurodevelopment with the three fundamental embryonic layers². Remak was able to utilize rabbit spinal roots and study their neurodevelopment along with his three embryonic layers, and it was through these layers he was able to describe the myelin sheath in his first paper². As many more discoveries with myelin followed his discovery, he would be able to offer great insight into each of them due to his fundamental understanding of myelin.

Sources:

1 Britannica, The Editors of Encyclopaedia. "Robert Remak". Encyclopedia Britannica, 25 Aug. 2021, https://www.britannica.com/biography/Robert-Remak. Accessed 4 April 2022.

2 Boullerne A. I. (2016). The history of myelin. Experimental neurology, 283(Pt B), 431–445. https://doi.org/10.1016/j.expneurol.2016.06.005

3 https://media.springernature.com/full/springer-static/image/art%3A10.1007%2Fs00415-012-6761-6/MediaObjects/415_2012_6761_Figa_HTML.jpg

The Discovery of Myelin

castillo219 — 2022-04-04 18:52:48 UTC

Andreas Vesalius is one of the biggest contributors to the field of neuroscience. He was the first to have been recognized for discovering white matter itself back in the 16^th century¹. Van Leeuwenhoek would then follow Vesalius and observe myelinated fibers for the first time in the year 1717¹. Ultimately, Robert Remak would be the final individual who claimed the fame for myelinated and unmyelinated axon fibers. Remak was able to solidify the existence of myelinated fibers by originally coined the term “Remaks Fibers” for unmyelinated nerve fibers in 1836, which had not yet been previously discovered².

The image above shows the depiction of an unmyelinated axon on the left and a myelinated axon on the right³.

Sources:

1) Boullerne AI. The history of myelin. Exp Neurol. 2016 Sep;283(Pt B):431-45. doi: 10.1016/j.expneurol.2016.06.005. Epub 2016 Jun 8. PMID: 27288241; PMCID: PMC5010938.

2) Grzybowski, A., & Pietrzak, K. (2013). Robert Remak (1815-1865). Journal of neurology, 260(6), 1696–1697. https://doi.org/10.1007/s00415-012-6761-6

3) https://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/14463663/f1_susuki_fig1.jpg

Multiple Sclerosis history & its effect on Myelin

castillo219 — 2022-04-04 19:33:57 UTC

Multiple Sclerosis (MS) is the commonest non-traumatic disease that affects young adults¹. It is disease in which the immune system degrades the myelin around the myelinated axons of the central nervous system, which ultimately disrupts communication between the brain and the body¹. was first discovered in 1868 by Jean-Martin Charcot, a French scientist who contributed very much to neuroscience². Charcot discovered MS by performing an autopsy on a patient named Luc who succumbed to this disease³. Charcot observed many sclerotic plaques throughout the brain and spinal cord and noticed that they were all identical no matter where they were³. He then examined another patient who was alive, but experiencing symptoms similar to Luc, and when they passed he performed another autopsy to confirm his hypothesis of MS³.

Sources:

1) Communications, H. (2020, February 26). History of Multiple Sclerosis. MSAA. https://mymsaa.org/ms-information/overview/history/

2) Dobson, R. and Giovannoni, G. (2019), Multiple sclerosis – a review. Eur J Neurol, 26: 27-40. https://doi.org/10.1111/ene.13819

3) Zalc B. (2018). One hundred and fifty years ago Charcot reported multiple sclerosis as a new neurological disease. Brain : a journal of neurology, 141(12), 3482–3488. https://doi.org/10.1093/brain/awy287

4) https://www.news-medical.net/image.axd?picture=2016%2F8%2FMultiple_Sclerosis_shutterstock_239380201.jpg

Theodor Schwann & his Schwann Cell

castillo219 — 2022-04-04 20:08:09 UTC

The discovery of the myelin sheath opened up many doors that would lead to more discoveries of the nervous system. Myelin would eventually then be classified into two types based on its location within the body: Oligodendrocytes in the central nervous system (CNS) and Schwann Cells in the peripheral nervous system (PNS)¹. Theodor Schwann would be the individual who discovered the Schwann Cell that resides in the PNS in 1838. Theodor Schwann was a German physiologist who made many contributions to science². He would be a key component to the proposition of the Cell theory which helped give a lot of fundamental understandings of cells². Theodor discovered Schwann Cells by investigating striated muscle in the upper esophagus and looking at the myelin that covered the axons in this region³.

Sources:

1) Morell P, Quarles RH. The Myelin Sheath. In: Siegel GJ, Agranoff BW, Albers RW, et al., editors. Basic Neurochemistry: Molecular, Cellular and Medical Aspects. 6th edition. Philadelphia: Lippincott-Raven; 1999. Available from: https://www.ncbi.nlm.nih.gov/books/NBK27954/

2) "Theodor Schwann ." Encyclopedia of World Biography. . Encyclopedia.com. 28 Mar. 2022 <https://www.encyclopedia.com>.

3) Britannica, The Editors of Encyclopaedia. "Theodor Schwann". Encyclopedia Britannica, 7 Jan. 2022, https://www.britannica.com/biography/Theodor-Schwann. Accessed 4 April 2022.

4) https://upload.wikimedia.org/wikipedia/commons/a/a5/Theodor_Schwann_Litho.jpg

Carl Weigert & the Myelin Stain

castillo219 — 2022-04-05 01:07:55 UTC

Carl Weigert was a German pathologist². He is accredited for his discovery of the myelin stain. Weigert was very knowledgeable about topics in pathology, with examples being coagulation necrosis and the pathogenesis of tuberculosis¹. He then delved into histology and devoted a lot of time in this discipline and made many contributions¹. The Weigert stain is what he devised in 1885, and this stain involves the treatment of nervous tissue with potassium dichromate to preserve myelin lipids, which are then stained with hematoxylin for visualizing fiber pathways².

The image above shows a cross section of the medulla oblongata that has been stained with the Weigert myelin stain³.

Sources:

1) Wohlrab F, Henoch U. Zum Leben und Wirken von Carl Weigert (1845-1904) in Leipzig 1878-1885 [The life and work of Carl Weigert (1845-1904) in Leipzig 1878-1885]. Zentralbl Allg Pathol. 1988;134(8):743-51. German. PMID: 3068935.

2) Weigert Stain. (2009). SpringerLink. https://link.springer.com/referenceworkentry/10.1007/978-3-540-29678-2_6444?error=cookies_not_supported&code=1fac95fe-56eb-4f06-8821-fc4a4a4046e9

3) https://i.pinimg.com/originals/17/e4/60/17e460b610db0d1da0139d675e9c1976.jpg

Contemporary Entry: Exercise, Diet, Myelin

castillo219 — 2022-04-05 02:05:15 UTC

Much more research has been done on the importance of myelin within our bodies. Myelin is important for the conduction of nerve impulses between the brain and spinal cord which allow for the human body to perform its desired actions¹. Damage to myelin in neurological injury and disease (e.g. multiple sclerosis) can negatively impact the health of the brain and the body¹. CNS health has been growing in popularity and many research studies were performed to learn about increasing CNS longevity.

Researchers at the Mayo Clinic Neuroregeneration and Neurorehabilitation Lab examined how dietary fat intake affect the production of myelin, oligodendrocytes in the CNS specifically¹. High fat and high sugar consumption can be negatively impactful toward myelin, even though myelin itself is composed of fat, but if the adequate amount is consumed it can lead to significant glial cell myelination¹.

Exercise is also shown to help benefit the CNS and also modulate myelin function¹. Undergoing a high-fat diet along with exercise training can increase myelin protein expression which is essential for a healthy CNS¹.

As modern neuroscience continues to progress, more avenues can be travelled down to learn more ways to keep the brain healthy. Constant discoveries are being made for myelin health, so its only a matter of time before more research breakthroughs in this topic occur.

Sources:

1) Analyzing the role of diet and exercise in myelin production - Mayo Clinic. (2020, April 23). N/A. https://www.mayoclinic.org/medical-professionals/physical-medicine-rehabilitation/news/analyzing-the-role-of-diet-and-exercise-in-myelin-production/mac-20429394

2) https://www.mayoclinic.org/-/media/kcms/gbs/patient-consumer/images/2016/10/10/17/50/myelinfig2lg.jpg