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Neuroepithelial Cells: Cells of epithelial origin possessing specialized sensory functions. They include cells that are found in the Taste buds; Olfactory mucosa; Cochlea; and Neuroepithelial bodies.
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Microfabrication of Chip-sized Scaffolds for Three-dimensional Cell cultivation

1Institute for Biological Interfaces, Karlsruhe Research Centre, 2Institute for BioMedical Technology, University of Twente, 3Department of Materials Research, Institute for Heavy Ion Research, 4Institute of Microstructure Technology, Karlsruhe Research Centre, 5Institute for Micro Process Engineering, Karlsruhe Research Centre

JoVE 699


 Biology

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Title Cell Encapsulation by Droplets

1Bio-Acoustic-MEMS Laboratory in Medicine (BAMM), HST-Center for Bioengineering, Brigham and Women's, Harvard Medical School, 2Bio-Acoustic-MEMS Laboratory in Medicine (BAMM), HST-Center for Bioengineering, Brigham and Women's Hospital, 3Brigham and Women's Hospital, Harvard Medical School, 4Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology; Center for Biomedical Engineering, Department of Medicine, Brigham and Women's Hospital


 Biology

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Making Solutions in the Laboratory

JoVE 5030

The ability to successfully make solutions is a basic laboratory skill performed in virtually all biological and chemical experiments. A solution is a homogenous mixture of solute dissolved in bulk liquid known as the solvent. Solutions can be described by their solute concentration, a measure of how much solute is present per unit of solution. In this video, a step-by-step procedure for how to make a water-based, or aqueous, solution for biological applications is presented. The video discusses how to calculate and measure the amount of solute needed for a given volume of solution. Methods for dissolving the solute in purified water and adjusting the pH of the solution are shown. Proper addition of the quantity sufficient (QS) to reach the desired volume is demonstrated with respect to the meniscus before discussing methods for sterilizing the solution. Applications of making solutions are presented through the discussion of several commonly used biological solutions, such as phosphate buffered saline (PBS), and their uses in biological research. These solutions are buffers that mimic physiological pH and osmolarity of cellular fluids.


 General Laboratory Techniques

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Introduction to Fluorescence Microscopy

JoVE 5040

Fluorescence microscopy is a very powerful analytical tool that combines the magnifying properties of light microscopy with visualization of fluorescence. Fluorescence is a phenomenon that involves absorbance and emission of a small range of light wavelengths by a fluorescent molecule known as a fluorophore. Fluorescence microscopy is accomplished in conjunction with the basic light microscope by the addition of a powerful light source, specialized filters, and a means of fluorescently labeling a sample. This video describes the basic principles behind fluorescence microscopy including the mechanism of fluorescence, the Stoke’s shift, and photobleaching. It also gives examples of the numerous ways to fluorescently label a sample including the use of fluorescently tagged antibodies and proteins, nucleic acid fluorescent dyes with, and the addition of naturally fluorescent proteins to a specimen. The major components of the fluorescence microscope including a xenon or mercury light source, light filters, the dichroic mirror, and use of the shutter to illuminate the sample are all described. Finally, examples of some of the many applications for fluorescence microscopy are shown.


 General Laboratory Techniques

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Using a Hemacytometer to Count Cells

JoVE 5048

Many biomedical experiments require manipulation of a known quantity of cells, in order to achieve accurate, reproducible, and statistically-relevant data. Therefore, learning how to count cells is a particularly essential technique for any successful biomedical scientist. The most common way to count cells is by using a hemacytometer - an instrument that bears two laser-etched grids, which aid in the enumeration of an aliquot cells under a simple light microscope. This data can then be used to extrapolate the number of cells in experimental sample. This video will show how to: adjust the experimental sample concentration so that you are not trying to count too many – or too few – cells; how to use a hemacytometer to count a small (~10 μl) aliquot of cells; how to determine which quadrant of the hemacytometer laser grid to use for counting; how to calculate the total number of cells in your experimental sample, depending upon which quadrant was used; and how to determine the viability of your experimental cell population using trypan blue exclusion. Further, various experimental situations for which reliable and accurate determination of cell numbers is necessary, including an example using an automated cell counter, are also discussed.


 Basic Methods in Cellular and Molecular Biology

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Passaging Cells

JoVE 5052

Cell lines are frequently used in biomedical experiments, as they allow rapid culture and expansion of cell types for experimental analysis. Cell lines are cultured under similar conditions when compared to freshly-isolated, or primary, cells, but with some basic important differences: (i) cell lines require their own specific growth factor cocktails and (ii) their growth must be more closely monitored than primary cells, as the mutations that allow them to be grown indefinitely also can quickly lead to their overgrowth. Therefore, when a cell line reaches the point of growth in culture where it covers most of the bottom of the culture container, or about a 90% confluency, the cells must be resuspended, washed, used experimentally, frozen for later use, or re-seeded for further expansion in new culture containers. This video will demonstrate how to use media indicators to determine cell culture health, which reagents and equipment are useful for safely removing adherent cell lines from culture, and various methods for transferring these robustly expanding cells into new cultures will be discussed. Also demonstrated are methods for how to culture feeder cells (important for providing essential growth factors to cell lines) and how to expand large numbers of cell line cultures at once.


 Basic Methods in Cellular and Molecular Biology

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Bacterial Transformation: The Heat Shock Method

JoVE 5059

Transformation is the process that occurs when a cell ingests foreign DNA from its surroundings. Transformation can occur in nature in certain types of bacteria. In molecular biology, transformation is artificially reproduced in the lab via the creation of pores in bacterial cell membranes. Bacterial cells that are able to take up DNA from the environment are called competent cells. In the laboratory, bacterial cells can be made competent and DNA subsequently introduced by a procedure called the heat shock method. Heat shock transformation uses a calcium rich environment provided by calcium chloride to counteract the electrostatic repulsion between the plasmid DNA and bacterial cellular membrane. A sudden increase in temperature creates pores in the plasma membrane of the bacteria and allows for plasmid DNA to enter the bacterial cell. This video goes through a step-by-step procedure on how to create chemically competent bacteria, perform heat shock transformation, plate the transformed bacteria, and calculate transformation efficiency.


 Basic Methods in Cellular and Molecular Biology

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Bacterial Transformation: Electroporation

JoVE 5060

The term “transformation” refers cellular ingestion of foreign DNA. In nature, transformation can occur in certain types of bacteria. In molecular biology, however, transformation is artificially induced through the creation of pores in the bacterial cell walls. Bacterial cells that are able to take up DNA from the environment are called competent cells. Electrocompetent cells can be produced in the laboratory and transformation of these cells can be achieve via the application of an electrical field that creates pores in the cell wall through which DNA can pass. The video explains the equipment used in electroporation such as an electroporator and electroporation cuvette. The video also goes through a step-by-step procedure about how to create electrocompetent cells and electroporate cells of interest. Prediction of the success of a transformation of an experiment, by observing the time constant, as well as the importance of removing salt from the solutions when electroporating, are also mentioned.


 Basic Methods in Cellular and Molecular Biology

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The ELISA Method

JoVE 5061

An enzyme-linked immunosorbent assay (ELISA) is typically performed to detect the presence and/or amount of a target protein of interest within an experimental sample. Detection of the target protein is made possible by antibodies, which make the ELISA an immunoassay. Through a series of incubation and washing steps, these antibodies, which are frequently linked, or conjugated, to an enzyme, will detect protein coating the bottom of a well on a microtiter plate. When exposed to a substrate, antibody-bound enzyme will cause a color change, thereby indicating the presence of the protein-of-interest in the sample. In this video, the theory behind how ELISAs work is explained, including a discussion of both primary and secondary antibody binding and the importance of blocking steps. Theory is followed by practice, as the video progresses to an explanation of the step-by-step procedure. Finally, variations of the standard ELISA such as the sandwich and competitive ELISAs are introduced, and real world applications of this method, such as in over-the-counter pregnancy tests are explained.


 Basic Methods in Cellular and Molecular Biology

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Plasmid Purification

JoVE 5062

Plasmid purification is a technique used to isolate and purify plasmid DNA from genomic DNA, proteins, ribosomes, and the bacterial cell wall. A plasmid is a small, circular, double-stranded DNA that is used as a carrier of specific DNA molecules. When introduced into a host organism via transformation, a plasmid will be replicated, creating numerous copies of the DNA fragment under study. In this video, a step-by-step generalized procedure is described for how to perform plasmid purification. Plasmid purification includes three basic steps: growth of the bacterial culture, harvesting and lysis of the bacteria, and purification of the plasmid DNA. The video contains an explanation where the plasmid can be found in each step of the protocol and to quantitatively and qualitatively analyze plasmid DNA with a spectrophotometer and/or gel electrophoresis. There are different types of plasmid purification methods available, which are geared toward desired yield, plasmid copy number, and bacterial culture volume.


 Basic Methods in Cellular and Molecular Biology

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The Western Blot

JoVE 5065

Western Blotting is used to identify the presence of specific proteins in electrophoretically separated samples. Following separation by a technique known as sodium dodecyl sulfate polyacrylamide gel electrophoresis, or SDS-PAGE, western transfer is used to move proteins from a polyacrylamide gel onto a piece of membrane which traps the proteins in their respective locations. Next, the membranes are probed with antibodies in a process called immunboblotting. Immunoblotting uses antibody-protein and antibody-antibody binding through specific recognition sites, providing the high specificity required for identifying a single protein. The detection of antibodies takes place using reporter systems which includes the use of enzymes. Enzymes can be attached to the end of an antibody and react with substrates to produce changes in color or light. These signals can then be imaged and quantified using a process called densitometry. This video-article presents an overview of the western blot technique by describing western transfer, the use of antibody detection, and image analysis. The steps involved with western transfer such as the assembly of the transfer sandwich and transfer conditions are discussed in detail as well as the theory behind antibody binding and detection of those antibodies. The broad applications of this technique are described through severa


 Basic Methods in Cellular and Molecular Biology

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An Introduction to Transfection

JoVE 5068

Transfection is the process of inserting genetic material, such as DNA and double stranded RNA, into mammalian cells. The insertion of DNA into a cell enables the expression, or production, of proteins using the cells own machinery, whereas insertion of RNA into a cell is used to down-regulate the production of a specific protein by stopping translation. While the site of action for transfected RNA is the cytoplasm, DNA must be transported to the nucleus for effective transfection. There, the DNA can be transiently expressed for a short period of time, or become incorporated into the genomic DNA, where the change is passed on from cell to cell as it divides. This video describes the basics behind chemical mediated transfections and introduces some of the most commonly-used reagents, including charged lipids, polymers, and calcium phosphate. Each step is described from the preparation of cells for transfection through analysis of transfection efficiency. Additionally, the applications section of this video-article describes the use of electroporation and a biolistic transfection as alternative methods for introducing nucleic acid into mammalian cells. It also describes an advanced use of transfection where co-transfection of interfering RNA and DNA are introduced as a way to down-regulate a naturally occurring protein while at the same time producing a


 Basic Methods in Cellular and Molecular Biology

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Molecular Cloning

JoVE 5074

Molecular cloning is a set of methods, which are used to insert recombinant DNA into a vector - a carrier of DNA molecules that will replicate recombinant DNA fragments in host organisms. The DNA fragment, which may be a gene, can be isolated from a prokaryotic or eukaryotic specimen. Following isolation of the fragment of interest, or insert, both the vector and insert must be cut with restriction enzymes and purified. The purified pieces are joined together though a technique called ligation. The enzyme that catalyzes the ligation reaction is known as ligase. This video explains the major methods that are combined, in tandem, to comprise the overall molecular cloning procedure. Critical aspects of molecular cloning are discussed, such as the need for molecular cloning strategy and how to keep track of transformed bacterial colonies. Verification steps, such as checking purified plasmid for the presence of insert with restrictions digests and sequencing are also mentioned.


 Basic Methods in Cellular and Molecular Biology

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