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Thomas H Segall-Shapiro, Eduardo D Sontag, Christopher A Voigt
The internal environment of growing cells is variable and dynamic, making it difficult to introduce reliable parts, such as promoters, for genetic engineering. Here, we applied control-theoretic ideas to design promoters that maintained constant levels of expression at any copy number. Theory predicts that independence to copy number can be achieved by using an incoherent feedforward loop (iFFL) if the negative regulation is perfectly non-cooperative. We engineered iFFLs into Escherichia coli promoters using transcription-activator-like effectors (TALEs)...
March 19, 2018: Nature Biotechnology
Xiaosa Li, Ying Wang, Yajing Liu, Bei Yang, Xiao Wang, Jia Wei, Zongyang Lu, Yuxi Zhang, Jing Wu, Xingxu Huang, Li Yang, Jia Chen
The targeting range of CRISPR-Cas9 base editors (BEs) is limited by their G/C-rich protospacer-adjacent motif (PAM) sequences. To overcome this limitation, we developed a CRISPR-Cpf1-based BE by fusing the rat cytosine deaminase APOBEC1 to a catalytically inactive version of Lachnospiraceae bacterium Cpf1. The base editor recognizes a T-rich PAM sequence and catalyzes C-to-T conversion in human cells, while inducing low levels of indels, non-C-to-T substitutions and off-target editing.
March 19, 2018: Nature Biotechnology
Ryan Rosenberry, Susie Chung, Michael D Nelson
Exercise represents a major hemodynamic stress that demands a highly coordinated neurovascular response in order to match oxygen delivery to metabolic demand. Reactive hyperemia (in response to a brief period of tissue ischemia) is an independent predictor of cardiovascular events and provides important insight into vascular health and vasodilatory capacity. Skeletal muscle oxidative capacity is equally important in health and disease, as it determines the energy supply for myocellular processes. Here, we describe a simple, non-invasive approach using near-infrared spectroscopy to assess each of these major clinical endpoints (reactive hyperemia, neurovascular coupling, and muscle oxidative capacity) during a single clinic or laboratory visit...
February 20, 2018: Journal of Visualized Experiments: JoVE
Johannes A Eble
The dissociation constant describes the interaction between two partners in the binding equilibrium and is a measure of their affinity. It is a crucial parameter to compare different ligands, e.g., competitive inhibitors, protein isoforms and mutants, for their binding strength to a binding partner. Dissociation constants are determined by plotting concentrations of bound versus free ligand as binding curves. In contrast, titration curves, in which a signal that is proportional to the concentration of bound ligand is plotted against the total concentration of added ligand, are much easier to record...
February 15, 2018: Journal of Visualized Experiments: JoVE
Tara Nietzold, Bradley M West, Michael Stuckelberger, Barry Lai, Stefan Vogt, Mariana I Bertoni
The quantification of X-ray fluorescence (XRF) microscopy maps by fitting the raw spectra to a known standard is crucial for evaluating chemical composition and elemental distribution within a material. Synchrotron-based XRF has become an integral characterization technique for a variety of research topics, particularly due to its non-destructive nature and its high sensitivity. Today, synchrotrons can acquire fluorescence data at spatial resolutions well below a micron, allowing for the evaluation of compositional variations at the nanoscale...
February 17, 2018: Journal of Visualized Experiments: JoVE
Barun Das, Jashdeep Bhattacharjee, Preeti, Alaknanda Mishra, Kshama Jain, Srikanth Iyer, Ashwani Kesarwani, Parul Sahu, Prakriti Sinha, Perumal Nagarajan, Pramod Upadhyay
Partial hepatectomy is a versatile and reproducible method to study liver regeneration and the effect of cell based therapeutics in various pathological conditions. Partial hepatectomy also facilitates the increased engraftment and proliferation of transplanted cells by accelerating neovascularization and cell migration towards the liver. Here, we describe a simple protocol for performing 30% hepatectomy and transplantation of cells in the spleen of a non-obese diabetic/severe combined immunodeficient NOD.SCID (NOD...
February 10, 2018: Journal of Visualized Experiments: JoVE
Shereen M Hamza, John E Hall
Renal sympathetic nerves contribute significantly to both physiological and pathophysiological phenomena. Evaluating renal sympathetic nerve activity (RSNA) is of great interest in many areas of research such as chronic kidney disease, hypertension, heart failure, diabetes and obesity. Unequivocal assessment of the role of the sympathetic nervous system is thus imperative for proper interpretation of experimental results and understanding of disease processes. RSNA has been traditionally measured in anesthetized rodents, including mice...
February 14, 2018: Journal of Visualized Experiments: JoVE
Andrew K Fuller, Benjamin D Bice, Ashlee R Venancio, Olivia M Crowley, Ambur M Staab, Stephanie J Georges, Julio R Hidalgo, Annika V Warncke, Melinda L Angus-Hill
Several recent studies have illustrated the beneficial effects of living in an enriched environment on improving human disease. In mice, environmental enrichment (EE) reduces tumorigenesis by activating the mouse immune system, or affects tumor bearing animal survival by stimulating the wound repair response, including improved microbiome diversity, in the tumor microenvironment. Provided here is a detailed procedure to assess the effects of environmental enrichment on the biodiversity of the microbiome in a mouse colon tumor model...
February 28, 2018: Journal of Visualized Experiments: JoVE
Renee Wei-Yan Chow, Paola Lamperti, Emily Steed, Francesco Boselli, Julien Vermot
During embryogenesis, cells undergo dynamic changes in cell behavior, and deciphering the cellular logic behind these changes is a fundamental goal in the field of developmental biology. The discovery and development of photoconvertible proteins have greatly aided our understanding of these dynamic changes by providing a method to optically highlight cells and tissues. However, while photoconversion, time-lapse microscopy, and subsequent image analysis have proven to be very successful in uncovering cellular dynamics in organs such as the brain or the eye, this approach is generally not used in the developing heart due to challenges posed by the rapid movement of the heart during the cardiac cycle...
February 20, 2018: Journal of Visualized Experiments: JoVE
Michael D Guthrie, Donald L Gilbert, David A Huddleston, Ernest V Pedapati, Paul S Horn, Stewart H Mostofsky, Steve W Wu
We describe the development of a reproducible, child-friendly motor response inhibition task suitable for online Transcranial Magnetic Stimulation (TMS) characterization of primary motor cortex (M1) excitability and inhibition. Motor response inhibition prevents unwanted actions and is abnormal in several neuropsychiatric conditions. TMS is a non-invasive technology that can quantify M1 excitability and inhibition using single- and paired-pulse protocols and can be precisely timed to study cortical physiology with high temporal resolution...
February 8, 2018: Journal of Visualized Experiments: JoVE
Jing Huang, Peng Guo, Marsha A Moses
The acquisition of the angiogenic phenotype is an essential component of the escape from tumor dormancy. Although several classic in vitro assays (e.g., proliferation, migration, and others) and in vivo models have been developed to investigate and characterize angiogenic and non-angiogenic cell phenotypes, these methods are time and labor intensive, and often require expensive reagents and instruments, as well as significant expertise. In a recent study, we used a novel quantitative phase imaging (QPI) technique to conduct time-lapse and labeling-free characterizations of angiogenic and non-angiogenic human osteosarcoma KHOS cells...
February 16, 2018: Journal of Visualized Experiments: JoVE
Federica Cavalera, Mario Zanoni, Valeria Merico, Thi Thu Hien Bui, Martina Belli, Lorenzo Fassina, Silvia Garagna, Maurizio Zuccotti
Infertility clinics would benefit from the ability to select developmentally competent vs. incompetent oocytes using non-invasive procedures, thus improving the overall pregnancy outcome. We recently developed a classification method based on microscopic live observations of mouse oocytes during their in vitro maturation from the germinal vesicle (GV) to the metaphase II stage, followed by the analysis of the cytoplasmic movements occurring during this time-lapse period. Here, we present detailed protocols of this procedure...
March 3, 2018: Journal of Visualized Experiments: JoVE
Sho Kurihara, Masato Fujioka, Tomohiko Yoshida, Makoto Koizumi, Kaoru Ogawa, Hiromi Kojima, Hirotaka James Okano
Hearing research has long been facilitated by rodent models, although in some diseases, human symptoms cannot be recapitulated. The common marmoset (Callithrix jacchus) is a small, easy-to-handle New World monkey which has a similar anatomy of the temporal bone, including the middle ear ossicular chains and inner ear to humans, than in comparison with that of rodents. Here, we report a reproducible, safe, and rational surgical approach to the cochlear round window niche for the drug delivery to the inner ear of the common marmoset...
February 27, 2018: Journal of Visualized Experiments: JoVE
Jacey L Janz Vernoski, Jack R Bjorkland, Talia J Kramer, Steven T Oczak, Alexandra L Borstad
Proprioception may be the least well measured of all contributors to the neural control of movement. New precise, reliable measures of proprioception are needed for clinical diagnosis of impairment, and to measure outcomes of proprioceptive training. The purpose of this simple, non-invasive method is to temporarily knockdown upper limb proprioception in healthy adults, to an extent that would be useful in the development and testing of upper limb proprioception measures. Knockdown models have two main advantages over studying humans with impaired proprioception: participant availability and the ability to control the extent of impairment across participants...
March 3, 2018: Journal of Visualized Experiments: JoVE
Joshua N Webb, Caroline Dong, Andres Bernal, Giuliano Scarcelli
The goal of this protocol is to mimic the biomechanics of physiological accommodation in a cost-efficient, practical manner. Accommodation is achieved through the contraction of the ciliary body and relaxation of zonule fibers, which results in the thickening of the lens necessary for near vision. Here, we present a novel, simple method in which accommodation is replicated by tensing the zonules connected to the lens capsule via a manual lens stretcher (MLS). This method monitors the radial stretching achieved by a lens when subjected to a consistent force and allows for a comparison of accommodating lenses, which can be stretched, to non-accommodating lenses, which cannot be stretched...
February 23, 2018: Journal of Visualized Experiments: JoVE
María Andrea Hernández-Castañeda, Smart Mbagwu, Kehinde Adebayo Babatunde, Michael Walch, Luis Filgueira, Pierre-Yves Mantel
Malaria is a life-threatening disease caused by Plasmodium parasites, with P. falciparum being the most prevalent on the African continent and responsible for most malaria-related deaths globally. Several factors including parasite sequestration in tissues, vascular dysfunction, and inflammatory responses influence the evolution of the disease in malaria-infected people. P. falciparum-infected red blood cells (iRBCs) release small extracellular vesicles (EVs) containing different kinds of cargo molecules that mediate pathogenesis and cellular communication between parasites and host...
February 14, 2018: Journal of Visualized Experiments: JoVE
Xinyi Ding, Yuxiang Sun, Yanming Chen, Wanchuan Ding, Steven Emory, Tianhao Li, Zixing Xu, Ning Han, Jun Wang, Gang Ruan
Micellar nanocrystals (micelles with encapsulated nanocrystals) have become an emerging major class of nanobiomaterials. We describe a method of fabricating micellar nanocrystals based on combining top-down electrospray, bottom-up self-assembly, and solvent-based structure control. This method involves first using electrospray to generate uniform ultrafine liquid droplets, each of which functions as a micro-reactor in which self-assembly reaction occurs forming micellar nanocrystals, with the structures (micelle shape and nanocrystal encapsulation) controlled by the organic solvent used...
February 11, 2018: Journal of Visualized Experiments: JoVE
Marija D Ivanovic, Jovana Petrovic, Andrej Savic, Goran Gligoric, Marjan Miletic, Miodrag Vukcevic, Bosko Bojovic, Ljupco Hadzievski, Tom D P Allsop, David J Webb
The ventilators involved in non-invasive mechanical ventilation commonly provide ventilator support via a facemask. The interface of the mask with a patient promotes air leaks that cause errors in the feedback information provided by a pneumatic sensor and hence patient-ventilator asynchrony with multiple negative consequences. Our objective is to test the possibility of using chest-wall motion measured by an optical fibre-grating sensor as a more accurate non-invasive ventilator triggering mechanism.
 Approach: The basic premise of our approach is that the measurement accuracy can be improved by using a triggering signal that precedes pneumatic triggering in the neuro-ventilatory coupling sequence...
March 19, 2018: Physiological Measurement
Güldane Cengiz Seval, Pervin Topçuoğlu, Taner Demirer
Hematopoietic stem cell transplantation is an established treatment for patients with a wide range of malignant and nonmalignant conditions. Noninfectious pulmonary complications still remain a leading cause of morbidity and mortality in these patients. Treating hematopoietic stem cell transplantation recipients with noninfectious pulmonary complications is still challenging, and the current treatment armamentarium and strategies are not adequate for patients receiving hematopoietic stem cell transplantation...
March 15, 2018: Balkan Medical Journal
Zoheir Elkahtib
BACKGROUND: Most health-care organisations are increasingly interested in assessing the quality of their services. Patient satisfaction has a central role in the quality assessment in health care because it reflects the appropriateness of services from the clients' perspectives. The aim of this study was to assess the level of satisfaction in patients with non-communicable diseases (mainly diabetes and hypertension) who receive services from UNRWA health centres in Gaza governorates. METHODS: In this cross-sectional study we chose a random sample of participants who presented to the randomly selected six health centres for treatment of non-communicable diseases...
February 21, 2018: Lancet
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