Currently, most of the in vitro cell research is performed on rigid tissue culture polystyrene (~1 GPa), while most cells in the body are attached to a matrix that is elastic and much softer (0.1 -100 kPa). Since such stiffness mismatch greatly affects cell responses, there is a strong interest in developing hydrogel materials that span a wide range of stiffness to serve as cell substrates. Polyacrylamide gels, which are inexpensive and cover the stiffness range of all soft tissues in the body, are the hydrogel of choice for many research groups. However, polyacrylamide gel preparation is lengthy, tedious, and only suitable for small batches. Here, we describe an assay which by utilizing a permanent flexible plastic film as a structural support for the gels, enables the preparation of polyacrylamide gels in a multiwell plate format. The technique is faster, more efficient, and less costly than current methods and permits the preparation of gels of custom sizes not otherwise available. As it doesn't require any specialized equipment, the method could be easily adopted by any research laboratory and would be particularly useful in research focused on understanding stiffness-dependent cell responses. Video LinkThe video component of this article can be found at
Carbon nanotube (CNT)-hydrogel composites are attractive for a variety of neural tissue engineering and drug delivery applications as well as biosensor coatings, transducers and leads.Both materials contribute unique and beneficial properties to the composites. Hydrogels are an excellent mimic of the extracellular matrix due to their hydrophilicity, viscoelasticity and biocompatibility. CNTs, on the other hand, can impart electroconductivity to otherwise insulating materials, improve mechanical stability and guide neuronal cell behavior as well as elicit axon regeneration. Not surprisingly, there has been a surge in the development of various CNT-hydrogel composites including both natural and synthetic polymers. Here, we describe a CNT-polyethylene glycol (PEG) hydrogel composite where the CNTs are entrapped in the hydrogel phase during gelation. The hydrogel crosslinking reaction is based on Michael-type addition which is ideal for in situ cell and protein encapsulation. To adequately disperse the highly hydrophobic CNTs in the aqueous polymer solution, we used sonication and surfactants, where bovine serum albumin was found to be an effective and non-cytotoxic dispersant. We demonstrate that the inclusion of the CNTs impeded the hydrogel crosslinking leading to longer gelation times, higher swelling and porosity, and lower storage modulus above a threshold CNT concentration. As anticipated, composite hydrogel resistivity decreased with the incorporation of CNTs and was dependent on both CNT loading and dispersion. Importantly, unlike the PEG hydrogel alone, the PEG-CNT hydrogel composite was capable of supporting high neural cell viability where the CNTs provided sites for cell attachment.
Polyacrylamide (PAA) hydrogels have become a widely used tool whose easily tunable mechanical properties, biocompatibility, thermostability, and chemical inertness make them invaluable in many biological applications, such as cell mechanosensitivity studies. Currently, preparation of PAA gels involves mixtures of acrylamide, bisacrylamide, a source of free radicals, and a chemical stabilizer. This method, while generally well accepted, has its drawbacks: long polymerization times, unstable and toxic reagents, and tedious preparation. Alternatively, PAA gels could be made by free radical polymerization (FRP) using ultraviolet (UV) photopolymerization, a method which is quicker, less tedious, and less toxic. Here, we describe a simple strategy based on total UV energy for determining the optimal UV crosslinking conditions that lead to optimal hydrogel modulus.
Currently, most of the in vitro cell research is performed on rigid tissue culture polystyrene (~1 GPa), while most cells in the body are attached to a matrix that is elastic and much softer (0.1 -100 kPa). Since such stiffness mismatch greatly affects cell responses, there is a strong interest in developing hydrogel materials that span a wide range of stiffness to serve as cell substrates. Polyacrylamide gels, which are inexpensive and cover the stiffness range of all soft tissues in the body, are the hydrogel of choice for many research groups. However, polyacrylamide gel preparation is lengthy, tedious, and only suitable for small batches. Here, we describe an assay which by utilizing a permanent flexible plastic film as a structural support for the gels, enables the preparation of polyacrylamide gels in a multiwell plate format. The technique is faster, more efficient, and less costly than current methods and permits the preparation of gels of custom sizes not otherwise available. As it doesn't require any specialized equipment, the method could be easily adopted by any research laboratory and would be particularly useful in research focused on understanding stiffness-dependent cell responses. Video LinkThe video component of this article can be found at http://www.jove.com/video/52643/ 12 Several promising high-throughput hydrogel technologies have been developed, including PEG-based microarrays, 13 microfluidic devices for the production of agarose hydrogel microbeads, 14 or micro and nano-rods where stiffness is modulated by the diameter and height of the microrods. 15 However, the technologies to prepare such substrates are sophisticated and available to limited number of laboratories. Much research involving stiffness modulated cell responses utilizes polyacrylamide (PA) gels which are not only inexpensive and simple to implement, but also exhibit a physiologically relevant range of Young's modulus, namely 0.3 -300 kPa. [16][17][18][19][20][21][22] However, existing methods to fabricate PA gels for cell culture are labor intensive and consequently prepared in small batches. Some of the difficulties associated with the preparation of PA gels as cell substrates stem from the requirement that the gels have to be prepared: 1) in the absence of oxygen to allow complete polymerization, 2) with a flat and smooth surface to permit uniform cell attachment and spreading, and 3) permanently affixed to the bottom of the cell culture dish to prevent floating.Several groups have attempted to produce PA gels for cell culture in large batches. Semler et al. prepared thick sheets of PA gels which were then "cut" with a hole punch and placed into 96-well plates. 23 However, this method is limited to stiffer gels, i.e., > 1 kPa in Young's modulus, because softer gels are "sticky", difficult to cut, and easily damaged. Mih et al. developed a more sophisticated technique which allows the gels to be directly polymerized in a glass-bottom multiwell plate. 6 This was achieved by pouring the gel solutions into functionalized gla...
Central etiologies of bilateral vocal cord paralysis leading to respiratory stridor are uncommon, as they require bilateral disruption of the laryngeal motor fibers. Here we present a young woman with multiple vascular risk factors, including ischemic stroke in the right medulla occurring 3 months prior, who presented with acute inspiratory stridor. All respiratory parameters were normal including arterial blood gas, and neck and pulmonary imaging. Direct laryngoscopy showed bilaterally bowed vocal cords, with decreased mobility and paradoxical adduction with each inspiratory cycle. On the third hospital day, neurological signs including a right hemiparesis became evident. Brain magnetic resonance imaging showed a diffusion restriction in the left medial pons likely disrupting the laryngeal motor fibers to the ponto‐medullary neuronal network. In the absence of tracheobronchial obstruction, physicians should be alert to the central causes of stridor including ischemic stroke. Additionally, paradoxical movements of the vocal cords can be an ominous sign.
Introduction. A number of rare anatomical anomalies, including retroexternal iliac ureter, extrarenal calyces (ERCs), and vascular anomalies, were observed in a 96-year-old female cadaver during a routine dissection. Description. A markedly dilated left extrarenal pelvis (ERP) with a diameter of 3.15 cm was noticed. Three major calyces were found outside of the normal-sized left kidney. The abdominal aorta (AA), instead of normal bifurcation, branched to the right common, left external, and left internal iliac arteries. The median sacral artery was a direct branch from the right common iliac artery. No hydronephrosis was observed on the affected side, and no urinary tract anomalies were observed on the right side. Significance. The retroiliac megaureter is a rare congenital anomaly, with fewer than 25 cases reported to date. Additionally, the ERCs are amongst the rarest anomalies of the renal collecting system. Further, the current case is one of few reported cases where the particular branching pattern of the AA was observed. The combination of such anatomical anomalies is rare, and the relationship between them is unclear. Common clinical manifestations of retroiliac ureters are the results of ureteric obstruction, hydronephrosis, and secondary infection. Precise knowledge of anomalies of the kidney and urinary tract can help radiologists and surgeons make a definitive diagnosis and prevent inadvertent injury during surgery.
Objective The rise of coronavirus disease 2019 (COVID-19) from Wuhan, China, in December 2019 has spread to more than 188 countries and has affected more than 13 million people. In response to this crisis, recommendations by the World Health Organization have changed the practice of current medicine, but there is little research as to how high-volume ambulatory specialties such as ophthalmology are adapting. The purpose of this study is to determine how ophthalmology practices are reacting and changing during the COVID-19 pandemic. Methods Approval was obtained from Saint Louis University School of Medicine Institutional Review Board. An anonymous survey was made on Google Forms and distributed to ophthalmologists throughout the world. Questions were divided into five sections: demographics, general questions, inpatient care/consults, practice management, and personal impact. The survey was opened on March 31, 2020, and closed on April 12, 2020. Statistical analysis was performed using Microsoft Excel. Results A total of 494 responders from 42 countries completed the survey. Respondents were predominantly practicing ophthalmologists (85%), with the next highest demographic being ophthalmology trainees (8%). Fear of spreading COVID-19 to patients or loved ones was the highest source of anxiety among practitioners across all practice settings and continental location (p = 0.003). The second source of anxiety varied, with private practitioners identifying financial difficulty compared with employed clinicians listing self-contamination. Anxiety levels were the same throughout all practice settings, ages, and subspecialties (p = 0.2527). Ophthalmologists listed ophthalmological Web sites/societies, discussion with colleagues, and social media as primary sources of guidance with no difference based on practice setting (p = 0.143). Finally, all continents increased their application of telemedicine as a patient care modality, with North America expanding significantly more than other continents. Conclusion The COVID-19 pandemic has drastically changed ophthalmology practice and has added a high level of stress to ophthalmologists globally. These results demonstrate that clinicians are largely alike across age group, country, and specialty, but key differences in source of anxiety and in application of telemedicine highlight diversity in culture and reaction to the pandemic.
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