Aşağıdaki iletişim kuralları Maryland Üniversitesi Kurumsal hayvan bakım ve kullanım Komitesi gibi altında Kurumsal değerlendirme Komitesi kabul edilir. İletişim kurallarını federal, eyalet ve yerel standartlara ve Biyogüvenlik University of Maryland ilkesine göre bu kurallar yola çıktı.
1. göz örnek diseksiyon
<ol><li>
Bir göz örnek yerel mezbaha veya doku bankasından edinin. Hemen tüm göz küre aldıysanız, objektif, ekli zonules ve camsı ayıklayın. Not: aşağıda açıklanan belirli ayrıntıları domuz ve insan gözleri ilgilidir.<ol>
<li>Dezenfekte Cerrahi makas ve forseps kullanarak, kesmek ve sklera çevreleyen tüm aşırı doku kaldırın.</li>
		<li>Sıkıca yan tarafında göz tutun ve jilet kullanarak, gözün kornea uzak 3 mm sol tarafındaki küçük bir kesi yapmak. Göz içinde Vitre ulaştınız için yeterince derin kesim yapmak.</li>
		<li>Makas kullanarak, dikkatle göz çevresi insizyon daha fazla kesin. Objektif delinme kaçının. Temsili resim Resim 2içindeAgösterilir.</li>
		<li>Gözün dış çevresi kesilmiş oldu kez forseps kullanarak göz posterior doku çıkarın. Objektif, zonules, silier beden ve ekli Vitre Forseps ile izole et. Bir temsili resim Şekil 2' deBgösterilir.</li>
		<li>Objektif düz MLS üzerinde yatıyordu makas ve forseps kullanarak aşırı Vitre kaldır. Not: kornea nakli durumlarda cerrahi kornea düğme kullanılır ve dünyanın geri kalanı araştırma amaçlı kullanılabilir. Ancak, bu kısmi küre hala objektif sedye Kur doku hazırlanmasında kullanılan. Arka elde edilen yalnızca, yalnızca adım 1.1.4–1.1.5 gerçekleştirin.</li>
	</ol>
</li>
	<li>30 dk için % 15 çamaşır suyu çözümündeki tüm makineleri sonrası diseksiyon dezenfekte.</li>
</ol>2. deneme manuel Lens sedye Meclisi
<ol><li>Orada kalır böylece ayakkabı girinti arka duvarına ve ayakkabı kendisi arasında bir 5 mm boşluk 10 mm ayakkabı dipleri ve karşılık gelen ayakkabı başında MLS alt plaka yerleştirin.</li>
	<li>Beraber tabakları dayama üst ve alt plaka hizalamak; aygıt şimdi uzatılmamış durumda.</li>
	<li>Tabakları plaka çalışması ve stoper vida alt plaka tarafında bulunan deliğe yerleştirin.</li>
	<li>Üsse doğru plaka kutu ilanı ve İngiliz anahtarını hizalanmış girintiler yerleştirin.</li>
	<li>Ayakkabı sözleşme ve ayakkabı özgün uzatılmamış konumuna döndürmek için geri saatin tersi yönde Döndür için durdurma vida ulaşıncaya kadar İngiliz anahtarını saat yönünde çevir.</li>
</ol>3. Lens montajı
<ol><li>5 mm boşluk kalıntıları arasında ayakkabı girinti ve ayakkabı kendisini arka duvarına 10 mm ayakkabı tabanları MLS alt plaka içine ekleyin.</li>
	<li>Ayakkabı objektif Merkez delik destek veriyor eğri forseps kullanarak, ayıklanan objektif yüzünü alt plaka ortasına yerleştirin.</li>
	<li>Ayakkabı karşılık gelen üst yerine, yalnızca zonules ve camsı kırpma oturtun. Görsel olarak objektif merkezli olarak kalmasını sağlamak alt plaka üzerinde mümkün olduğunca.</li>
	<li>2.3-2.4 adımları yineleyin.</li>
</ol>4. Lens ölçümü
<ol><li>Videolar ve resimler germe işlemi yakalamak için bir görüntüleme sistemi aparatı hemen üstüne yerleştirin. Post-processing doğru boyut ve ölçek görüntüleri için resim çerçeve içinde bir cetvel eklediğinizden emin olun. Not: Herhangi bir uygun görüntüleme sistemi bu adım için yeterlidir; Burada kullanıyoruz bir 12 megapiksel, autofocusing smartphone örnekten bir ayak.</li>
	<li>Sıkıca henüz sorunsuz, İngiliz anahtarı yönünde objektif germek için döndürün. Şekil 3 uzatılmamış ve gergin Devlet Temsilcisi görüntüleri gösterir.</li>
	<li>Gergin objektif fotoğrafçılık sonra anahtarı örnek istirahat durumuna geri yüklemek için saat yönünün tersi yönde döndür. Not: Ölçüm lens lensin su kaybı en aza indirmek için zamanında gerçekleştirilir zorunludur.</li>
	<li>Açıkça objektif nihai dinlenme durumunu fotoğraf.</li>
</ol>5. veri analizi
<ol><li>ImageJ için resim yükleme ve şekil 4Agösterildiği gibi objektif en az 40 puan çevresi için "nokta" özelliğini kullanın. Seçili her noktasında verim için "Analiz" → "Tedbir" seçeneğini kullanın.</li>
	<li>(Yazılım örneğin MATLAB kullanarak) konumu Puan bir RADIUS ve şekil 4Bgösterildiği gibi uygun ki verim için uygun. Piksel yarıçapı ve hata fotoğraflandı cetvel kullanarak ölçümleri dönüştürün.</li>
	<li>Eşleştirilmiş iki kuyruklu t-bireysel bir objektif önce ve sonra MLS germe karşılaştırmak için sınama gerçekleştirin.</li>
</ol>

<ol>
	<li>Von Helmholtz, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Uber+die+akkommodation+des+auges.">Uber die akkommodation des auges.</a> Arch Ophthal. 1, 1-74 (1855).</li><li>Schachar, R. A., Black, T. D., Kash, R. L., Cudmore, D. P., Schanzlin, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mechanism+of+accommodation+and+presbyopia+in+the+primate.">The mechanism of accommodation and presbyopia in the primate.</a> Ann Ophthalmol. 27, 58-67 (1995).</li><li>Glasser, A., Campbell, C. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Presbyopia+and+the+optical+changes+in+the+human+crystalline+lens+with+age.">Presbyopia and the optical changes in the human crystalline lens with age.</a> Vision Res. 38 (2), 209-229 (1998).</li><li>Reilly, M. A., Hamilton, P. D., Perry, G., Ravi, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+the+behavior+and+natural+and+refilled+porcine+lenses+in+a+robotic+lens+stretcher.">Comparison of the behavior and natural and refilled porcine lenses in a robotic lens stretcher.</a> Exp Eye Res. 88, 483-494 (2009).</li><li>Langenbucher, A., Huber, S., Nguyen, N. X., Seitz, B., Gusek-Schneider, G. C., K&#252;chle, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+accommodation+after+implantation+of+an+accommodating+posterior+chamber+intraocular+lens.">Measurement of accommodation after implantation of an accommodating posterior chamber intraocular lens.</a> J Cataract Refract Surg. 29 (4), 677-685 (2003).</li><li>Ehrmann, K., Ho, A., Parel, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomechanical+analysis+of+the+accommodative+apparatus+in+primates.">Biomechanical analysis of the accommodative apparatus in primates.</a> Clin Exp Optom. 91 (4), 411 (2008).</li><li>Pinilla Cort&#233;s, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+Protocols+for+Ex+Vivo+Lens+Stretching+Tests+to+Investigate+the+Biomechanics+of+the+Human+Accommodation+Apparatus.">Experimental Protocols for Ex Vivo Lens Stretching Tests to Investigate the Biomechanics of the Human Accommodation Apparatus.</a> Invest Ophthalmol Vis Sci. 56 (5), 2926 (2015).</li><li>Fisher, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+elastic+constants+of+the+human+lens.">The elastic constants of the human lens.</a> J Physiol. 212 (1), 147-180 (1971).</li><li>Eppig, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomechanical+eye+model+and+measurement+setup+for+investigating+accommodating+intraocular+lenses.">Biomechanical eye model and measurement setup for investigating accommodating intraocular lenses.</a> Z Med Ohys. 23 (2), 144-152 (2013).</li><li>Manns, F., Parel, , et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Response+of+Human+and+Monkey+Lenses+in+a+Lens+Stretcher.">Response of Human and Monkey Lenses in a Lens Stretcher.</a> Invest Ophthalmol Vis Sci. 48 (7), 3260 (2007).</li><li>Scarcelli, G., Kim, P., Yun, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+measurement+of+age-related+stiffening+in+the+crystalline+lens+by+Brillouin+optical+microscopy.">In vivo measurement of age-related stiffening in the crystalline lens by Brillouin optical microscopy.</a> Biophys J. 101 (6), 1539-1545 (2011).</li><li>Besner, S., Scarcelli, G., Pineda, R., Yun, S. -. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+Vivo+Brillouin+Analysis+of+the+Aging+Crystalline+Lens.">In Vivo Brillouin Analysis of the Aging Crystalline Lens.</a> Invest Ophthalmol Vis Sci. 57 (13), 5093 (2016).</li><li>Cortes, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+Protocols+for+Ex+Vivo+Lens+Stretching+Tests+to+Investigate+the+Biomechanics+of+the+Human+Accommodation+Apparatus.">Experimental Protocols for Ex Vivo Lens Stretching Tests to Investigate the Biomechanics of the Human Accommodation Apparatus.</a> Invest Ophthalmol Vis Sci. 56 (5), 2926-2932 (2015).</li><li>Bernal, A., Parel, J. -. M., Manns, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+for+Posterior+Zonular+Fiber+Attachment+on+the+Anterior+Hyaloid+Membrane.">Evidence for Posterior Zonular Fiber Attachment on the Anterior Hyaloid Membrane.</a> Invest Ophthalmol Vis Sci. 47 (11), 4708 (2006).</li><li>Kammel, R., Ackermann, R., Mai, T., Damm, C., Nolte, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pig+Lenses+in+a+Lens+Stretcher.">Pig Lenses in a Lens Stretcher.</a> Optom Vis Sci. 89 (6), 908-915 (2012).</li><li>Hahn, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+Ex+Vivo+Porcine+Lens+Shape+During+Simulated+Accommodation,+Before+and+After+fs-Laser+Treatment.">Measurement of Ex Vivo Porcine Lens Shape During Simulated Accommodation, Before and After fs-Laser Treatment.</a> Invest Ophthalmol Vis Sci. 56 (9), 5332-5343 (2015).</li><li>D'Antin, J. C., Cortes, L. P., Montenegro, G. A., Barraquer, R. I., Michael, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+a+portable+manual+stretching+device+to+simulate+accommodation.">Evaluation of a portable manual stretching device to simulate accommodation.</a> Acta Ophthalmol. 93 (255), (2015).</li><li>Pierscionek, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Age-related+response+of+human+lenses+to+stretching+forces.">Age-related response of human lenses to stretching forces.</a> Exp Eye Res. 60 (3), 325-332 (1995).</li><li>Marussich, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+Crystalline+Lens+Volume+During+Accommodation+in+a+Lens+Stretcher.">Measurement of Crystalline Lens Volume During Accommodation in a Lens Stretcher.</a> Invest Ophthalmol Vis Sci. 56 (8), 4239 (2015).</li><li>Martinez-Enriquez, E., P&#233;rez-Merino, P., Velasco-Ocana, M., Marcos, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=OCT-based+full+crystalline+lens+shape+change+during+accommodation+in+vivo.">OCT-based full crystalline lens shape change during accommodation in vivo.</a> Biomed Opt Exp. 8 (2), 918-933 (2017).</li></ol>

AB Bioniko Consulting LLC hissedarıdır.

Sedye için örnek çift objektif konaklama yeteneği bir çift parçalı sıkma mekanizması kullanarak okuyan bir doğru ve verimli şekilde sağlamak için yeni bir yöntem tasarladılar. Konaklama sırasında objektif rahatlatır ve rahatlama zonular lifleri1,2,4,19yanıt olarak çapı azalır. Yöntem sıkma ve zonular iplik gerginlik kontrol bu olgu üzerinde odaklanır. Bu nedenle, doğr...

Konaklama insan gözü tarafından dinamik olarak keskin odak uzak ya da yakın mesafelerde nesneleri görmek için onun kristal mercek şeklini ayarlamak için süreç olduğunu. Konaklama özünde biyomekanik bir süreçtir. Nöro uyarıcı bir kuvvet silier vücut üzerine ve objektif kapsül1,2çevresi eklemek zonule lifleri için silier kaslar üretmek. Farklı teoriler konaklama biyomekanik arkasında olmakla birlikte, en yaygın olarak kabul edilen Helmholtz hipotezdir. Göre objektif bir doğal gerilmiş durumda uzak nesneleri odak için en iyi lens en ince şeklinde karşılık gelen hipotezdir. Odağı daha yakın nesneleri değiştirmek için silier Kaslar sözleşme ve zonular lifleri rahat. Buna karşılık, objektif, anterior ve posteiror yüzey eğrilikleri artan kalınlaşır. Bu vizyon, bu nedenle, daha kısa bir odak uzaklığı1için gerekli olan Dioptrik güç artışa karşılık gelir.
Uyum yeteneği Presbiyopi adında bir koşulu ile zaman içinde güvenilir değil. Herkes 50 yaşında tarafından etkileyen, Presbiyopi dinamik olarak uzak mesafeler3kapatmak için odaktan değiştiremiyorsanız göz yapar. Presbiyopi mücadele etmek için geçerli düzeltici lensler ve Çift odaklı gözlüklerin gibi pasif yöntemlerdir. Kaç uçak yakın nesneleri odaklanmak için bir yetenek artırırken, böyle pasif tedaviler objektif4,5dinamik odak yeteneği geri yükleyemezsiniz. Presbiyopi verimli bir şekilde tedavi veya muhtemelen önlemek için konaklama daha iyi anlamak için devam eden bir gerek yoktur.
Objektif konaklama çalışmaya, cihazların bir dizi fenomen ex vivo4,6,7,8,9simülasyonu için geliştirilmiştir. İplik diskler ilk lens merkezkaç kuvvetler8üzerinden germe izlemek için tanıtıldı. Daha sadakatle fenomen çoğaltmak için objektif germe cihazlar yavaş yavaş tanıttı yenilikçi ve. Kullanarak bir objektif sedye, Mannlar ve ark. objektif lens güç ve Ekvator çapı9böyle birleştiriliyor süre karşılamak için gerekli güç ile karakterizedir. Objektif lens şekli silier vücut3,10,11,12yanıt eşit bir güç olarak azaltılmış bir değişiklik sonuçlanan yaş ile stiffens geçerli anlaşılmasıdır.
Geçerli objektif sedye kez ve elektronik ve programlanabilir germe fiyatlar, uygulama karmaşık bir kuruluma dahil tüm kadavra göz küresi6,7,10,13gerektirir. Bu gereksinim deneye göz başına üzerinde $500,00 başına maliyet artar ve örnek kullanılabilirliği azalır. Burada göz arka yaklaşık 200,00 $ toplamları gibi objektif konaklama düşük maliyetle eşlemek için bir yöntem mevcut. Süre bugün kullanılan birçok aygıt daha az gelişmiş teknik sonuçlar ödün vermeden daha maliyet etkin ve adoptable olduğunu. Bu yöntem şekil 1' de tasvir bir manuel lens sedye (MLS) etrafında merkezli ve benzersiz bir sıkma sistemi lens çapını genişletmek için zonular lifleri ve Radyal kıvırma yöntemi kullanır. Protokol fizyolojik doğruluğunu Bernal ve arkbulgular tarafından doğrulanır., kim hangi anterior ve posteiror zonular lifleri için objektif kapsül14bağlı yol okudu. Sadece objektif, zonule ve silier gövde gerektiren özel Ayakkabı Tasarım kullanarak, fizyolojik konaklama kopyalayan tarafından objektif biyomekanik araştırmayı amaçladık.

<table><tbody><tr><td>Manual Lens Stretcher</td><td>Bioniko</td><td>MLS</td><td>Different animal species will require different shoe sizes</td></tr><tr><td>Porcine Eye Samples</td><td>George G. Ruppersberger; slaughterhouse</td><td>N/A</td><td>Whole eyeballs were obtained</td></tr><tr><td>Human Eye Samples</td><td>The National Disease Research Interchange</td><td>N/A</td><td>Posterior poles without corneas were ordered</td></tr><tr><td>Dissecting Scissors (5 1/2&#039;&#039; Straight)</td><td>Electron Microsopy Sciences</td><td>72960</td><td></td></tr><tr><td>Tissue Forceps (4 1/2&#039;&#039;)</td><td>Electron Microsopy Sciences</td><td>72960</td><td></td></tr><tr><td>iPhone 6s</td><td>Apple</td><td>N/A</td><td>Any imaging system with ~0.1 mm resolution will work</td></tr><tr><td>Sodium Hypochorite</td><td>Clorox</td><td>Clorox Regular-Bleach</td><td>Any disinfectant will work</td></tr></tbody></table>

simulating the mechanics of lens accommodation via a manual lens stretcher

Bu iletişim kuralı, fizyolojik konaklama biyomekanik maliyet-etkin ve pratik bir şekilde taklit için hedeftir. Konaklama silier vücut kasılması ve objektifin vizyon için gerekli kalinlasma sonuçlanan gevşeme zonule liflerinin yoluyla elde edilir. Burada, mevcut bir roman, basit yöntem konaklama lens kapsülü manuel lens sedye (MLS) üzerinden bağlı zonules gerilmesini tarafından çoğaltılır. Bu yöntem Radyal bir lens için tutarlı bir güç maruz elde germe izler ve accomodating, gergin olabilir sigara accomodating lensler için gergin olabilir lensler bir karşılaştırma sağlar. Önemlisi, sedye zonules doğrudan ve böylece sadece objektif, zonules ve silier vücut yerine tüm dünyada örnek gerektiren göz, sklera çiftler. Bu fark anlamlı bir tüm dünyada elde etmek göre yaklaşık % 62 donör kadavra lensler edinme maliyetini düşürebilir.

Domuz gözler, Presbiyopi4,15, germe objektif ile çalışmak için ortak bir örnek elde edilen, (n = 10) yerel bir mezbaha ve bu iletişim kuralı konaklama yetenek lenslerin gözlemlemek için kullanıldı. Şekil 5 A önce ve sonra MLS germe domuz objektif karşılaştırmasını gösterir. Gergin zaman objektif RADIUS bir ortalama 0,19 ± 0,07 mm artış oldu (p < 0.001)...

Watch this Scientific Journal Video about Simulating the Mechanics of Lens Accommodation via a Manual Lens Stretcher at JoVE.com

Simulating the Mechanics of Lens Accommodation via a Manual Lens Stretcher

Manuel Lens sedye ile Lens konaklama mekaniği simüle

Biz objektif konaklama manuel lens sedye kullanarak okuyan verimli bir yöntem mevcut. Objektif uzanan zonules çekerek fizyolojik konaklama lens kapsülü, böylece, bağlı iletişim kuralı taklit eder.

The goal of this protocol is to mimic the biomechanics of physiological accommodation in a cost-efficient, practical manner. Accommodation is achieved ...

simulating-mechanics-lens-accommodation-via-manual-lens

Research

JoVE Journal

Bioengineering

6.7K Görüntüleme.  University of Maryland. Biz objektif konaklama manuel lens sedye kullanarak okuyan verimli bir yöntem mevcut. Objektif uzanan zonules çekerek fizyolojik konaklama lens kapsülü, böylece, bağlı iletişim kuralı taklit eder.

Video: Simulating the Mechanics of Lens Accommodation via a Manual Lens Stretcher

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers

Single-molecule techniques for stretching DNA of contour lengths less than a kilobase are fraught with experimental difficulties. However, many interesting biological events such as histone binding and protein-mediated looping of DNA1,2, occur on this length scale. In recent years, the mechanical properties of DNA have been shown to play a significant role in fundamental cellular processes like the packaging of DNA into compact nucleosomes and chromatin fibers3,4. Clearly, it is then important to understand the mechanical properties of short stretches of DNA. In this paper, we provide a practical guide to a single-molecule optical tweezing technique that we have developed to study the mechanical behavior of DNA with contour lengths as short as a few hundred basepairs.
The major hurdle in stretching short segments of DNA is that conventional optical tweezers are generally designed to apply force in a direction lateral to the stage5,6, (see Fig. 1). In this geometry, the angle between the bead and the coverslip, to which the DNA is tethered, becomes very steep for submicron length DNA. The axial position must now be accounted for, which can be a challenge, and, since the extension drags the microsphere closer to the coverslip, steric effects are enhanced. Furthermore, as a result of the asymmetry of the microspheres, lateral extensions will generate varying levels of torque due to rotation of the microsphere within the optical trap since the direction of the reactive force changes during the extension.
Alternate methods for stretching submicron DNA run up against their own unique hurdles. For instance, a dual-beam optical trap is limited to stretching DNA of around a wavelength, at which point interference effects between the two traps and from light scattering between the microspheres begin to pose a significant problem. Replacing one of the traps with a micropipette would most likely suffer from similar challenges. While one could directly use the axial potential to stretch the DNA, an active feedback scheme would be needed to apply a constant force and the bandwidth of this will be quite limited, especially at low forces.
We circumvent these fundamental problems by directly pulling the DNA away from the coverslip by using a constant force axial optical tweezers7,8. This is achieved by trapping the bead in a linear region of the optical potential, where the optical force is constant-the strength of which can be tuned by adjusting the laser power. Trapping within the linear region also serves as an all optical force-clamp on the DNA that extends for nearly 350 nm in the axial direction. We simultaneously compensate for thermal and mechanical drift by finely adjusting the position of the stage so that a reference microsphere stuck to the coverslip remains at the same position and focus, allowing for a virtually limitless observation period.

We illustrate the use of a constant force axial optical tweezers to explore the mechanical properties of short DNA molecules. By stretching DNA axially, we minimize steric hindrances and artifacts arising in conventional lateral manipulation, allowing us to study DNA molecules as short as ~100 nm.

Sabit Kuvvet Eksenel Optik cımbız ile DNA Kısa Diziler Stretching

Single-molecule techniques for stretching DNA of contour lengths  less than a kilobase are fraught with experimental difficulties. However, many ...

Biyomühendislik

Stretching Micropatterned Cells on a PDMS Membrane

Mechanical forces exerted on cells and/or tissues play a major role in numerous processes. We have developed a device to stretch cells plated on a PolyDiMethylSiloxane (PDMS) membrane, compatible with imaging. This technique is reproducible and versatile. The PDMS membrane can be micropatterned in order to confine cells or tissues to a specific geometry. The first step is to print micropatterns onto the PDMS membrane with a deep UV technique. The PDMS membrane is then mounted on a mechanical stretcher. A chamber is bound on top of the membrane with biocompatible grease to allow gliding during the stretch. The cells are seeded and allowed to spread for several hours on the micropatterns. The sample can be stretched and unstretched multiple times with the use of a micrometric screw. It takes less than a minute to apply the stretch to its full extent (around 30%). The technique presented here does not include a motorized device, which is necessary for applying repeated stretch cycles quickly and/or computer controlled stretching, but this can be implemented. Stretching of cells or tissue can be of interest for questions related to cell forces, cell response to mechanical stress or tissue morphogenesis. This video presentation will show how to avoid typical problems that might arise when doing this type of seemingly simple experiment.

This manuscript presents a technique to apply or release forces on adherent cells or tissues using unidirectional stretching.

PDMS Zarında Micropatterned Hücreler germe

Mechanical forces exerted on cells and/or tissues  play a major role in numerous processes. We have developed a device to stretch  cells plated on a ...

A Novel Stretching Platform for Applications in Cell and Tissue Mechanobiology

Tools that allow the application of mechanical forces to cells and tissues or that can quantify the mechanical properties of biological tissues have contributed dramatically to the understanding of basic mechanobiology. These techniques have been extensively used to demonstrate how the onset and progression of various diseases are heavily influenced by mechanical cues. This article presents a multi-functional biaxial stretching (BAXS) platform that can either mechanically stimulate single cells or quantify the mechanical stiffness of tissues. The BAXS platform consists of four voice coil motors that can be controlled independently. Single cells can be cultured on a flexible substrate that can be attached to the motors allowing one to expose the cells to complex, dynamic, and spatially varying strain fields. Conversely, by incorporating a force load cell, one can also quantify the mechanical properties of primary tissues as they are exposed to deformation cycles. In both cases, a proper set of clamps must be designed and mounted to the BAXS platform motors in order to firmly hold the flexible substrate or the tissue of interest. The BAXS platform can be mounted on an inverted microscope to perform simultaneous transmitted light and/or fluorescence imaging to examine the structural or biochemical response of the sample during stretching experiments. This article provides experimental details of the design and usage of the BAXS platform and presents results for single cell and whole tissue studies. The BAXS platform was used to measure the deformation of nuclei in single mouse myoblast cells in response to substrate strain and to measure the stiffness of isolated mouse aortas. The BAXS platform is a versatile tool that can be combined with various optical microscopies in order to provide novel mechanobiological insights at the sub-cellular, cellular and whole tissue levels.

We present in this article a novel stretching platform that can be used to investigate single cell responses to complex anisotropic biaxial mechanical deformation and quantify the mechanical properties of biological tissues.

Hücre ve Doku mechanobiology Applications A Novel Germe Platformu

Tools that allow the application of mechanical forces to cells and tissues or that can quantify the mechanical properties of biological tissues have ...

Live Cell Imaging during Mechanical Stretch

There is currently a significant interest in understanding how cells and tissues respond to mechanical stimuli, but current approaches are limited in their capability for measuring responses in real time in live cells or viable tissue. A protocol was developed with the use of a cell actuator to distend live cells grown on or tissues attached to an elastic substrate while imaging with confocal and atomic force microscopy (AFM). Preliminary studies show that tonic stretching of human bronchial epithelial cells caused a significant increase in the production of mitochondrial superoxide. Moreover, using this protocol, alveolar epithelial cells were stretched and imaged, which showed direct damage to the epithelial cells by overdistention simulating one form of lung injury in vitro. A protocol to conduct AFM nano-indentation on stretched cells is also provided.

A novel imaging protocol was developed using a custom motor-driven mechanical actuator to allow the measurement of real time responses to mechanical strain in live cells. Relevant to mechanobiology, the system can apply strains up to 20% while allowing near real-time imaging with confocal or atomic force microscopy.

Mekanik Stretch sırasında Canlı Hücre Görüntüleme

There is currently a significant interest in understanding how cells and tissues respond to mechanical stimuli, but current approaches are limited in ...

Synthesis of Soft Polysiloxane-urea Elastomers for Intraocular Lens Application

This study discusses a synthesis route for soft polysiloxane-based urea (PSU) elastomers for their applications as accommodating intraocular lenses (a-IOLs). Aminopropyl-terminated polydimethylsiloxanes (PDMS) were previously prepared via the ring-chain equilibration of the cyclic siloxane octamethylcyclotetrasiloxane (D4) and 1,3-bis(3-aminopropyl)-tetramethyldisiloxane (APTMDS). Phenyl groups were introduced into the siloxane backbone via the copolymerization of D4 and 2,4,6,8-tetramethyl-2,4,6,8-tetraphenyl-cyclotetrasiloxane (D4Me,Ph). These polydimethyl-methyl-phenyl-siloxane-block copolymers were synthesized for increasing the refractive indices of polysiloxanes. For applications as an a-IOL, the refractive index of the polysiloxanes must be equivalent to that of a young human eye lens. The polysiloxane molecular weight is controlled by the ratio of the cyclic siloxane to the endblocker APTMDS. The transparency of the PSU elastomers is examined by the transmittance measurement of films between 200 and 750 nm, using a UV-Vis spectrophotometer. Transmittance values at 750 nm (upper end of the visible spectrum) are plotted against the PDMS molecular weight, and &#62; 90% of the transmittance is observed until a molecular weight of 18,000 g&#183;mol&#8722;1. Mechanical properties of the PSU elastomers are investigated using stress-strain tests on die-cut dog-bone-shaped specimens. For evaluating mechanical stability, mechanical hysteresis is measured by repeatedly stretching (10x) the specimens to 5% and 100% elongation. Hysteresis considerably decreases with the increase in the PDMS molecular weight. In vitro cytotoxicity of some selected PSU elastomers is evaluated using an MTS cell viability assay. The methods described herein permit the synthesis of a soft, transparent, and noncytotoxic PSU elastomer with a refractive index approximately equal to that of a young human eye lens.

This study describes synthetic routes for aminopropyl-terminated polydimethylsiloxanes and polydimethyl-methyl-phenyl-siloxane-block copolymers and for soft polysiloxane-based urea (PSU) elastomers. It presents the application of PSUs as accommodating an intraocular lens. An evaluation method for in vitro cytotoxicity is also described.

Yumuşak Polysiloxane-üre elastomerler için göz içi Lens uygulama sentezi

This study discusses a synthesis route for soft polysiloxane-based urea (PSU) elastomers for their applications as accommodating intraocular lenses ...

Kimya

Production of a Strain-Measuring Device with an Improved 3D Printer

A traditional strain measurement sensor needs to be electrified and is susceptible to electromagnetic interference. In order to solve the fluctuations in the analog electrical signal in a traditional strain gauge operation, a new strain measurement method is presented here. It uses a photographic technique to display the strain change by amplifying the change of the pointer displacement of the mechanism. A visual polydimethylsiloxane (PDMS) lens with a focal length of 7.16 mm was added to a smartphone camera to generate a lens group acting as a microscope to capture images. It had an equivalent focal length of 5.74 mm. Acrylonitrile butadiene styrene (ABS) and nylon amplifiers were used to test the influence of different materials on the sensor performance. The production of the amplifiers and PDMS lens is based on improved 3D printing technology. The data obtained were compared with the results from finite element analysis (FEA) to verify their validity. The sensitivity of the ABS amplifier was 36.03 &plusmn; 1.34 &#181;&epsilon;/&#181;m, and the sensitivity of the nylon amplifier was 36.55 &plusmn; 0.53 &#181;&epsilon;/&#181;m.

This work presents a strain measurement sensor consisting of an amplification mechanism and a polydimethylsiloxane microscope manufactured using an improved 3D printer.

Geliştirilmiş 3D Yazıcılı Gerinim Ölçüm Cihazı Üretimi

A traditional strain measurement sensor needs to be electrified and is susceptible to electromagnetic interference. In order to solve the fluctuations in ...

Mühendislik

Controlled Strain of 3D Hydrogels under Live Microscopy Imaging

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized in vitro stretching methods. Various available systems use 2D substrate-based stretchers, while the accessibility of 3D techniques to strain soft hydrogels, is more restricted. Here, we describe a method that allows external stretching of soft hydrogels from their circumference, using an elastic silicone strip as the sample carrier. The stretching system utilized in this protocol is constructed from 3D-printed parts and low-cost electronics, making it simple and easy to replicate in other labs. The experimental process begins with polymerizing thick (&#62;100 &#956;m) soft fibrin hydrogels (Elastic Modulus of ~100 Pa) in a cut-out at the center of a silicone strip. Silicone-gel constructs are then attached to the printed-stretching device and placed on the confocal microscope stage. Under live microscopy the stretching device is activated, and the gels are imaged at various stretch magnitudes. Image processing is then used to quantify the resulting gel deformations, demonstrating relatively homogenous strains and fiber alignment throughout the gel&#8217;s 3D thickness (Z-axis). Advantages of this method include the ability to strain extremely soft hydrogels in 3D while executing in situ microscopy, and the freedom to manipulate the geometry and size of the sample according to the user&#8217;s needs. Additionally, with proper adaptation, this method can be used to stretch other types of hydrogels (e.g., collagen, polyacrylamide or polyethylene glycol) and can allow for analysis of cells and tissue response to external forces under more biomimetic 3D conditions.

The presented method involves uniaxial stretching of 3D soft hydrogels embedded in silicone rubber while allowing live confocal microscopy. Characterization of the external and internal hydrogel strains as well as fiber alignment are demonstrated. The device and protocol developed can assess the response of cells to various strain regimes.

Canlı Mikroskopi Görüntüleme Altında 3D Hidrojellerin Kontrollü Suşu

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized ...

Otomatik Sıkıştırma ile Domuz Oküler Lensinin Biyomekanik Karakterizasyonu

Automated Compression Testing of the Ocular Lens

The biomechanical properties of the ocular lens are essential to its function as a variable power optical element. These properties change dramatically with age in the human lens, resulting in a loss of near vision called presbyopia. However, the mechanisms of these changes remain unknown. Lens compression offers a relatively simple method for assessing the lens' biomechanical stiffness in a qualitative sense and, when coupled with appropriate analytical techniques, can help quantify biomechanical properties. A variety of lens compression tests have been performed to date, including both manual and automated, but these methods inconsistently apply key aspects of biomechanical testing such as preconditioning, loading rates, and time between measurements. This paper describes a fully automated lens compression test wherein a motorized stage is synchronized with a camera to capture the force, displacement, and shape of the lens throughout a preprogrammed loading protocol. A characteristic elastic modulus may then be calculated from these data. While demonstrated here using porcine lenses, the approach is appropriate for the compression of lenses of any species.

Yazar Spotlight: Yaşa Bağlı Lens Sertliği Değişikliklerinin Anlaşılmasını Geliştirmek 

We present an automated method for characterizing the effective elastic modulus of an ocular lens using a compression test.

Oküler lensin otomatik kompresyon testi

The biomechanical properties of the ocular lens are essential to its function as a variable power optical element. These properties change dramatically ...

Manuel Lens sedye ile Lens konaklama mekaniği simüle

Özet

Daha Fazla Video Keşfet

PLAYLIST