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Welcome to The Visible Embryo, a comprehensive educational resource on human development from conception to birth.

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Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
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Home | Pregnancy Timeline | News Alerts |News Archive Sep 3, 2013

 

"Noise-induced hearing loss, with accompanying tinnitus and sound hypersensitivity is a common condition which leads to communication problems and social isolation."
Xiaorui Shi, M.D., Ph.D., study author



PVM/Ms PVM/M modifies the production of PEDF

Perivascular resident macrophages (PVM/Ms) are hybrid cells with characteristcs of both macrophage (immune) and melanocyte (melanin-producing cells located in the bottom layer of the skin's epidermis, the middle layer of the eye, the inner ear, meninges, bones, and heart. Melanin is the pigment primarily responsible for skin color). Both cell types are critical for creating and maintaining the potential for hearing.

Image Credit: Perivascular-resident macrophage-like melanocytes in the inner ear are essential for the integrity of the intrastrial fluid–blood barrier





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Now hear this: Compound prevents noise-related hearing loss

New research suggests that excessive noise activates certain cells in the ear causing them to detach and damage the blood barrier.

Your mother was right when she warned you that loud music could damage your hearing, but now scientists have discovered exactly what gets damaged and how. In a research report published in the September 2013 issue of The FASEB Journal, scientists describe exactly what type of damage noise does to the inner ear, and provide insights into a compound that may prevent noise-related damage.

"Noise-induced hearing loss, with accompanying tinnitus and sound hypersensitivity is a common condition which leads to communication problems and social isolation. The goal of our study is to understand the molecular mechanisms well enough to mitigate damage from exposure to loud sound." Xiaorui Shi, M.D., Ph.D., study author, Department of Otolaryngology/Head and Neck Surgery, Oregon Hearing Research Center, Oregon Health and Science University in Portland, Oregon.

To make this discovery, Shi and colleagues used three groups of 6 - 8 week old mice, which consisted of a control group, a group exposed to broadband noise at 120 decibels for three hours a day for two days, and a third group given single-dose injections of pigment epithelium-derived factor (PEDF) prior to noise exposure.


Pigment epithelium-derived factor (PEDF) is a protein found in vertebrates that is currently being researched for the treatment of diseases like heart disease and cancer.

The cells that secrete PEDF in control animals showed characteristic branching, with the cells arranging in a self-avoidance pattern that provides good coverage of the capillary wall of the ear.

The morphology of the same cells in the animals exposed to wide-band noise, however, showed clear differences noise exposure caused changes in melanocytes located in the inner ear.


"Hearing loss over time robs people of their quality of life. It's easy to say that we should avoid loud noises, but in reality, this is not always possible. Front-line soldiers or first responders do not have time to worry about the long-term effects of loud noise when they are giving their all. If, however, a drug could be developed to minimize the negative effects of loud noises, it would benefit one and all."

Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal.

Abstract
Tissue perivascular resident macrophages (PVM/Ms), a hybrid cell type with characteristics of both macrophages and melanocytes, are critical for establishing and maintaining the endocochlear potential (EP) required for hearing. The PVM/Ms modulate expression of tight- and adherens-junction proteins in the endothelial barrier of the stria vascularis (intrastrial fluid-blood barrier) through secretion of a signaling molecule, pigment epithelium growth factor (PEDF). Here, we identify a significant link between abnormalities in PVM/Ms and endothelial barrier breakdown from acoustic trauma to the mouse ear. We find that acoustic trauma causes activation of PVM/Ms and physical detachment from capillary walls. Concurrent with the detachment, we find loosened tight junctions between endothelial cells and decreased production of tight- and adherens-junction protein, resulting in leakage of serum proteins from the damaged barrier. A key factor in the intrastrial fluid-blood barrier hyperpermeability exhibited in the mice is down-regulation of PVM/M modulated PEDF production. We demonstrate that delivery of PEDF to the damaged ear ameliorates hearing loss by restoring intrastrial fluid-blood barrier integrity. PEDF up-regulates expression of tight junction-associated proteins (ZO-1 and VE-cadherin) and PVM/M stabilizing neural cell adhesion molecule (NCAM-120). These studies point to the critical role PVM/Ms play in regulating intrastrial fluid-blood barrier integrity in healthy and noise-damaged ears.—Zhang, F., Dai, M., Neng, L., Zhang, J.H., Zhi, Z., Fridberger, A., Shi, X. Perivascular macrophage-like melanocyte responsiveness to acoustic trauma— a salient feature of strial barrier associated hearing loss.

Receive monthly highlights from The FASEB Journal by e-mail. Sign up at http://www.faseb.org/fjupdate.aspx. The FASEB Journal is published by the Federation of the American Societies for Experimental Biology (FASEB). It is among the most cited biology journals worldwide according to the Institute for Scientific Information and has been recognized by the Special Libraries Association as one of the top 100 most influential biomedical journals of the past century.

FASEB is composed of 27 societies with more than 110,000 members, making it the largest coalition of biomedical research associations in the United States. Our mission is to advance health and welfare by promoting progress and education in biological and biomedical sciences through service to our member societies and collaborative advocacy.

Details: Fei Zhang, Min Dai, Lingling Neng, Jin Hui Zhang, Zhongwei Zhi, Anders Fridberger, and Xiaorui Shi. Perivascular macrophage-like melanocyte responsiveness to acoustic trauma -- a salient feature of strial barrier associated hearing loss. FASEB J September 2013 27:3730-3740, doi:10.1096/fj.13-232892 ; http://www.fasebj.org/content/27/9/3730.abstract

Original press release: http://www.eurekalert.org/pub_releases/2013-08/foas-nht082913.php