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Pubmed Article
Optimal semelparity.
PLoS ONE
PUBLISHED: 01-17-2013
Semelparous organisms have a simple life cycle characterized by immediate death after reproduction. We assume that semelparous life histories can be separated into a juvenile non-reproductive period followed by an adult period during which reproduction is possible. We derive formulae for the optimal age and size at reproduction and for the optimal size of the offspring (e.g., seeds). Our main contribution is to determine the conditions under which the optimal size of the offspring does not depend on the optimal size at reproduction and vice versa.
Authors: Eva Wagner, Sören Brandenburg, Tobias Kohl, Stephan E. Lehnart.
Published: 10-15-2014
ABSTRACT
In cardiac myocytes a complex network of membrane tubules - the transverse-axial tubule system (TATS) - controls deep intracellular signaling functions. While the outer surface membrane and associated TATS membrane components appear to be continuous, there are substantial differences in lipid and protein content. In ventricular myocytes (VMs), certain TATS components are highly abundant contributing to rectilinear tubule networks and regular branching 3D architectures. It is thought that peripheral TATS components propagate action potentials from the cell surface to thousands of remote intracellular sarcoendoplasmic reticulum (SER) membrane contact domains, thereby activating intracellular Ca2+ release units (CRUs). In contrast to VMs, the organization and functional role of TATS membranes in atrial myocytes (AMs) is significantly different and much less understood. Taken together, quantitative structural characterization of TATS membrane networks in healthy and diseased myocytes is an essential prerequisite towards better understanding of functional plasticity and pathophysiological reorganization. Here, we present a strategic combination of protocols for direct quantitative analysis of TATS membrane networks in living VMs and AMs. For this, we accompany primary cell isolations of mouse VMs and/or AMs with critical quality control steps and direct membrane staining protocols for fluorescence imaging of TATS membranes. Using an optimized workflow for confocal or superresolution TATS image processing, binarized and skeletonized data are generated for quantitative analysis of the TATS network and its components. Unlike previously published indirect regional aggregate image analysis strategies, our protocols enable direct characterization of specific components and derive complex physiological properties of TATS membrane networks in living myocytes with high throughput and open access software tools. In summary, the combined protocol strategy can be readily applied for quantitative TATS network studies during physiological myocyte adaptation or disease changes, comparison of different cardiac or skeletal muscle cell types, phenotyping of transgenic models, and pharmacological or therapeutic interventions.
24 Related JoVE Articles!
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A Guided Materials Screening Approach for Developing Quantitative Sol-gel Derived Protein Microarrays
Authors: Blake-Joseph Helka, John D. Brennan.
Institutions: McMaster University .
Microarrays have found use in the development of high-throughput assays for new materials and discovery of small-molecule drug leads. Herein we describe a guided material screening approach to identify sol-gel based materials that are suitable for producing three-dimensional protein microarrays. The approach first identifies materials that can be printed as microarrays, narrows down the number of materials by identifying those that are compatible with a given enzyme assay, and then hones in on optimal materials based on retention of maximum enzyme activity. This approach is applied to develop microarrays suitable for two different enzyme assays, one using acetylcholinesterase and the other using a set of four key kinases involved in cancer. In each case, it was possible to produce microarrays that could be used for quantitative small-molecule screening assays and production of dose-dependent inhibitor response curves. Importantly, the ability to screen many materials produced information on the types of materials that best suited both microarray production and retention of enzyme activity. The materials data provide insight into basic material requirements necessary for tailoring optimal, high-density sol-gel derived microarrays.
Chemistry, Issue 78, Biochemistry, Chemical Engineering, Molecular Biology, Genetics, Bioengineering, Biomedical Engineering, Chemical Biology, Biocompatible Materials, Siloxanes, Enzymes, Immobilized, chemical analysis techniques, chemistry (general), materials (general), spectroscopic analysis (chemistry), polymer matrix composites, testing of materials (composite materials), Sol-gel, microarray, high-throughput screening, acetylcholinesterase, kinase, drug discovery, assay
50689
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Transabdominal Ultrasound for Pregnancy Diagnosis in Reeves' Muntjac Deer
Authors: Kelly D. Walton, Erin McNulty, Amy V. Nalls, Candace K. Mathiason.
Institutions: Colorado State University.
Reeves' muntjac deer (Muntiacus reevesi) are a small cervid species native to southeast Asia, and are currently being investigated as a potential model of prion disease transmission and pathogenesis. Vertical transmission is an area of interest among researchers studying infectious diseases, including prion disease, and these investigations require efficient methods for evaluating the effects of maternal infection on reproductive performance. Ultrasonographic examination is a well-established tool for diagnosing pregnancy and assessing fetal health in many animal species1-7, including several species of farmed cervids8-19, however this technique has not been described in Reeves' muntjac deer. Here we describe the application of transabdominal ultrasound to detect pregnancy in muntjac does and to evaluate fetal growth and development throughout the gestational period. Using this procedure, pregnant animals were identified as early as 35 days following doe-buck pairing and this was an effective means to safely monitor the pregnancy at regular intervals. Future goals of this work will include establishing normal fetal measurement references for estimation of gestational age, determining sensitivity and specificity of the technique for diagnosing pregnancy at various stages of gestation, and identifying variations in fetal growth and development under different experimental conditions.
Medicine, Issue 83, Ultrasound, Reeves' muntjac deer, Muntiacus reevesi, fetal development, fetal growth, captive cervids
50855
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A Novel Three-dimensional Flow Chamber Device to Study Chemokine-directed Extravasation of Cells Circulating under Physiological Flow Conditions
Authors: Valentina Goncharova, Sophia K. Khaldoyanidi.
Institutions: Torrey Pines Institute for Molecular Studies, Cascade LifeSciences Inc..
Extravasation of circulating cells from the bloodstream plays a central role in many physiological and pathophysiological processes, including stem cell homing and tumor metastasis. The three-dimensional flow chamber device (hereafter the 3D device) is a novel in vitro technology that recreates physiological shear stress and allows each step of the cell extravasation cascade to be quantified. The 3D device consists of an upper compartment in which the cells of interest circulate under shear stress, and a lower compartment of static wells that contain the chemoattractants of interest. The two compartments are separated by porous inserts coated with a monolayer of endothelial cells (EC). An optional second insert with microenvironmental cells of interest can be placed immediately beneath the EC layer. A gas exchange unit allows the optimal CO2 tension to be maintained and provides an access point to add or withdraw cells or compounds during the experiment. The test cells circulate in the upper compartment at the desired shear stress (flow rate) controlled by a peristaltic pump. At the end of the experiment, the circulating and migrated cells are collected for further analyses. The 3D device can be used to examine cell rolling on and adhesion to EC under shear stress, transmigration in response to chemokine gradients, resistance to shear stress, cluster formation, and cell survival. In addition, the optional second insert allows the effects of crosstalk between EC and microenvironmental cells to be examined. The translational applications of the 3D device include testing of drug candidates that target cell migration and predicting the in vivo behavior of cells after intravenous injection. Thus, the novel 3D device is a versatile and inexpensive tool to study the molecular mechanisms that mediate cellular extravasation.
Bioengineering, Issue 77, Cellular Biology, Biophysics, Physiology, Molecular Biology, Biomedical Engineering, Immunology, Cells, Biological Factors, Equipment and Supplies, Cell Physiological Phenomena, Natural Science Disciplines, Life Sciences (General), circulating cells, extravasation, physiological shear stress, endothelial cells, microenvironment, chemokine gradient, flow, chamber, cell culture, assay
50959
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Milk Collection Methods for Mice and Reeves' Muntjac Deer
Authors: Kassandra Willingham, Erin McNulty, Kelly Anderson, Jeanette Hayes-Klug, Amy Nalls, Candace Mathiason.
Institutions: Colorado State University.
Animal models are commonly used throughout research laboratories to accomplish what would normally be considered impractical in a pathogen’s native host. Milk collection from animals allows scientists the opportunity to study many aspects of reproduction including vertical transmission, passive immunity, mammary gland biology, and lactation. Obtaining adequate volumes of milk for these studies is a challenging task, especially from small animal models. Here we illustrate an inexpensive and facile method for milk collection in mice and Reeves’ muntjac deer that does not require specialized equipment or extensive training. This particular method requires two researchers: one to express the milk and to stabilize the animal, and one to collect the milk in an appropriate container from either a Muntjac or mouse model. The mouse model also requires the use of a P-200 pipetman and corresponding pipette tips. While this method is low cost and relatively easy to perform, researchers should be advised that anesthetizing the animal is required for optimal milk collection.
Basic Protocol, Issue 89, mouse, milk, murine, muntjac, doe
51007
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Barnes Maze Testing Strategies with Small and Large Rodent Models
Authors: Cheryl S. Rosenfeld, Sherry A. Ferguson.
Institutions: University of Missouri, Food and Drug Administration.
Spatial learning and memory of laboratory rodents is often assessed via navigational ability in mazes, most popular of which are the water and dry-land (Barnes) mazes. Improved performance over sessions or trials is thought to reflect learning and memory of the escape cage/platform location. Considered less stressful than water mazes, the Barnes maze is a relatively simple design of a circular platform top with several holes equally spaced around the perimeter edge. All but one of the holes are false-bottomed or blind-ending, while one leads to an escape cage. Mildly aversive stimuli (e.g. bright overhead lights) provide motivation to locate the escape cage. Latency to locate the escape cage can be measured during the session; however, additional endpoints typically require video recording. From those video recordings, use of automated tracking software can generate a variety of endpoints that are similar to those produced in water mazes (e.g. distance traveled, velocity/speed, time spent in the correct quadrant, time spent moving/resting, and confirmation of latency). Type of search strategy (i.e. random, serial, or direct) can be categorized as well. Barnes maze construction and testing methodologies can differ for small rodents, such as mice, and large rodents, such as rats. For example, while extra-maze cues are effective for rats, smaller wild rodents may require intra-maze cues with a visual barrier around the maze. Appropriate stimuli must be identified which motivate the rodent to locate the escape cage. Both Barnes and water mazes can be time consuming as 4-7 test trials are typically required to detect improved learning and memory performance (e.g. shorter latencies or path lengths to locate the escape platform or cage) and/or differences between experimental groups. Even so, the Barnes maze is a widely employed behavioral assessment measuring spatial navigational abilities and their potential disruption by genetic, neurobehavioral manipulations, or drug/ toxicant exposure.
Behavior, Issue 84, spatial navigation, rats, Peromyscus, mice, intra- and extra-maze cues, learning, memory, latency, search strategy, escape motivation
51194
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Measuring the Effects of Bacteria on C. Elegans Behavior Using an Egg Retention Assay
Authors: Mona Gardner, Mary Rosell, Edith M. Myers.
Institutions: Fairleigh Dickinson University.
C. elegans egg-laying behavior is affected by environmental cues such as osmolarity1 and vibration2. In the total absence of food C. elegans also cease egg-laying and retain fertilized eggs in their uterus3. However, the effect of different sources of food, especially pathogenic bacteria and particularly Enterococcus faecalis, on egg-laying behavior is not well characterized. The egg-in-worm (EIW) assay is a useful tool to quantify the effects of different types of bacteria, in this case E. faecalis, on egg- laying behavior. EIW assays involve counting the number of eggs retained in the uterus of C. elegans4. The EIW assay involves bleaching staged, gravid adult C. elegans to remove the cuticle and separate the retained eggs from the animal. Prior to bleaching, worms are exposed to bacteria (or any type of environmental cue) for a fixed period of time. After bleaching, one is very easily able to count the number of eggs retained inside the uterus of the worms. In this assay, a quantifiable increase in egg retention after E. faecalis exposure can be easily measured. The EIW assay is a behavioral assay that may be used to screen for potentially pathogenic bacteria or the presence of environmental toxins. In addition, the EIW assay may be a tool to screen for drugs that affect neurotransmitter signaling since egg-laying behavior is modulated by neurotransmitters such as serotonin and acetylcholine5-9.
Developmental Biology, Issue 80, Microbiology, C. elegans, Behavior, Animal, Microbiology, Caenorhabditis elegans, Enterococcus faecalis, egg-laying behavior, animal model
51203
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Characterization of Complex Systems Using the Design of Experiments Approach: Transient Protein Expression in Tobacco as a Case Study
Authors: Johannes Felix Buyel, Rainer Fischer.
Institutions: RWTH Aachen University, Fraunhofer Gesellschaft.
Plants provide multiple benefits for the production of biopharmaceuticals including low costs, scalability, and safety. Transient expression offers the additional advantage of short development and production times, but expression levels can vary significantly between batches thus giving rise to regulatory concerns in the context of good manufacturing practice. We used a design of experiments (DoE) approach to determine the impact of major factors such as regulatory elements in the expression construct, plant growth and development parameters, and the incubation conditions during expression, on the variability of expression between batches. We tested plants expressing a model anti-HIV monoclonal antibody (2G12) and a fluorescent marker protein (DsRed). We discuss the rationale for selecting certain properties of the model and identify its potential limitations. The general approach can easily be transferred to other problems because the principles of the model are broadly applicable: knowledge-based parameter selection, complexity reduction by splitting the initial problem into smaller modules, software-guided setup of optimal experiment combinations and step-wise design augmentation. Therefore, the methodology is not only useful for characterizing protein expression in plants but also for the investigation of other complex systems lacking a mechanistic description. The predictive equations describing the interconnectivity between parameters can be used to establish mechanistic models for other complex systems.
Bioengineering, Issue 83, design of experiments (DoE), transient protein expression, plant-derived biopharmaceuticals, promoter, 5'UTR, fluorescent reporter protein, model building, incubation conditions, monoclonal antibody
51216
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Accuracy in Dental Medicine, A New Way to Measure Trueness and Precision
Authors: Andreas Ender, Albert Mehl.
Institutions: University of Zürich.
Reference scanners are used in dental medicine to verify a lot of procedures. The main interest is to verify impression methods as they serve as a base for dental restorations. The current limitation of many reference scanners is the lack of accuracy scanning large objects like full dental arches, or the limited possibility to assess detailed tooth surfaces. A new reference scanner, based on focus variation scanning technique, was evaluated with regards to highest local and general accuracy. A specific scanning protocol was tested to scan original tooth surface from dental impressions. Also, different model materials were verified. The results showed a high scanning accuracy of the reference scanner with a mean deviation of 5.3 ± 1.1 µm for trueness and 1.6 ± 0.6 µm for precision in case of full arch scans. Current dental impression methods showed much higher deviations (trueness: 20.4 ± 2.2 µm, precision: 12.5 ± 2.5 µm) than the internal scanning accuracy of the reference scanner. Smaller objects like single tooth surface can be scanned with an even higher accuracy, enabling the system to assess erosive and abrasive tooth surface loss. The reference scanner can be used to measure differences for a lot of dental research fields. The different magnification levels combined with a high local and general accuracy can be used to assess changes of single teeth or restorations up to full arch changes.
Medicine, Issue 86, Laboratories, Dental, Calibration, Technology, Dental impression, Accuracy, Trueness, Precision, Full arch scan, Abrasion
51374
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Tissue Triage and Freezing for Models of Skeletal Muscle Disease
Authors: Hui Meng, Paul M.L. Janssen, Robert W. Grange, Lin Yang, Alan H. Beggs, Lindsay C. Swanson, Stacy A. Cossette, Alison Frase, Martin K. Childers, Henk Granzier, Emanuela Gussoni, Michael W. Lawlor.
Institutions: Medical College of Wisconsin, The Ohio State University, Virginia Tech, University of Kentucky, Boston Children's Hospital, Harvard Medical School, Cure Congenital Muscular Dystrophy, Joshua Frase Foundation, University of Washington, University of Arizona.
Skeletal muscle is a unique tissue because of its structure and function, which requires specific protocols for tissue collection to obtain optimal results from functional, cellular, molecular, and pathological evaluations. Due to the subtlety of some pathological abnormalities seen in congenital muscle disorders and the potential for fixation to interfere with the recognition of these features, pathological evaluation of frozen muscle is preferable to fixed muscle when evaluating skeletal muscle for congenital muscle disease. Additionally, the potential to produce severe freezing artifacts in muscle requires specific precautions when freezing skeletal muscle for histological examination that are not commonly used when freezing other tissues. This manuscript describes a protocol for rapid freezing of skeletal muscle using isopentane (2-methylbutane) cooled with liquid nitrogen to preserve optimal skeletal muscle morphology. This procedure is also effective for freezing tissue intended for genetic or protein expression studies. Furthermore, we have integrated our freezing protocol into a broader procedure that also describes preferred methods for the short term triage of tissue for (1) single fiber functional studies and (2) myoblast cell culture, with a focus on the minimum effort necessary to collect tissue and transport it to specialized research or reference labs to complete these studies. Overall, this manuscript provides an outline of how fresh tissue can be effectively distributed for a variety of phenotypic studies and thereby provides standard operating procedures (SOPs) for pathological studies related to congenital muscle disease.
Basic Protocol, Issue 89, Tissue, Freezing, Muscle, Isopentane, Pathology, Functional Testing, Cell Culture
51586
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Culturing Caenorhabditis elegans in Axenic Liquid Media and Creation of Transgenic Worms by Microparticle Bombardment
Authors: Tamika K. Samuel, Jason W. Sinclair, Katherine L. Pinter, Iqbal Hamza.
Institutions: University of Maryland, University of Maryland.
In this protocol, we present the required materials, and the procedure for making modified C. elegans Habituation and Reproduction media (mCeHR). Additionally, the steps for exposing and acclimatizing C. elegans grown on E. coli to axenic liquid media are described. Finally, downstream experiments that utilize axenic C. elegans illustrate the benefits of this procedure. The ability to analyze and determine C. elegans nutrient requirement was illustrated by growing N2 wild type worms in axenic liquid media with varying heme concentrations. This procedure can be replicated with other nutrients to determine the optimal concentration for worm growth and development or, to determine the toxicological effects of drug treatments. The effects of varied heme concentrations on the growth of wild type worms were determined through qualitative microscopic observation and by quantitating the number of worms that grew in each heme concentration. In addition, the effect of varied nutrient concentrations can be assayed by utilizing worms that express fluorescent sensors that respond to changes in the nutrient of interest. Furthermore, a large number of worms were easily produced for the generation of transgenic C. elegans using microparticle bombardment.
Molecular Biology, Issue 90, C. elegans, axenic media, transgenics, microparticle bombardment, heme, nutrition
51796
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The Generation of Higher-order Laguerre-Gauss Optical Beams for High-precision Interferometry
Authors: Ludovico Carbone, Paul Fulda, Charlotte Bond, Frank Brueckner, Daniel Brown, Mengyao Wang, Deepali Lodhia, Rebecca Palmer, Andreas Freise.
Institutions: University of Birmingham.
Thermal noise in high-reflectivity mirrors is a major impediment for several types of high-precision interferometric experiments that aim to reach the standard quantum limit or to cool mechanical systems to their quantum ground state. This is for example the case of future gravitational wave observatories, whose sensitivity to gravitational wave signals is expected to be limited in the most sensitive frequency band, by atomic vibration of their mirror masses. One promising approach being pursued to overcome this limitation is to employ higher-order Laguerre-Gauss (LG) optical beams in place of the conventionally used fundamental mode. Owing to their more homogeneous light intensity distribution these beams average more effectively over the thermally driven fluctuations of the mirror surface, which in turn reduces the uncertainty in the mirror position sensed by the laser light. We demonstrate a promising method to generate higher-order LG beams by shaping a fundamental Gaussian beam with the help of diffractive optical elements. We show that with conventional sensing and control techniques that are known for stabilizing fundamental laser beams, higher-order LG modes can be purified and stabilized just as well at a comparably high level. A set of diagnostic tools allows us to control and tailor the properties of generated LG beams. This enabled us to produce an LG beam with the highest purity reported to date. The demonstrated compatibility of higher-order LG modes with standard interferometry techniques and with the use of standard spherical optics makes them an ideal candidate for application in a future generation of high-precision interferometry.
Physics, Issue 78, Optics, Astronomy, Astrophysics, Gravitational waves, Laser interferometry, Metrology, Thermal noise, Laguerre-Gauss modes, interferometry
50564
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Assessing Differences in Sperm Competitive Ability in Drosophila
Authors: Shu-Dan Yeh, Carolus Chan, José M. Ranz.
Institutions: University of California, Irvine.
Competition among conspecific males for fertilizing the ova is one of the mechanisms of sexual selection, i.e. selection that operates on maximizing the number of successful mating events rather than on maximizing survival and viability 1. Sperm competition represents the competition between males after copulating with the same female 2, in which their sperm are coincidental in time and space. This phenomenon has been reported in multiple species of plants and animals 3. For example, wild-caught D. melanogaster females usually contain sperm from 2-3 males 4. The sperm are stored in specialized organs with limited storage capacity, which might lead to the direct competition of the sperm from different males 2,5. Comparing sperm competitive ability of different males of interest (experimental male types) has been performed through controlled double-mating experiments in the laboratory 6,7. Briefly, a single female is exposed to two different males consecutively, one experimental male and one cross-mating reference male. The same mating scheme is then followed using other experimental male types thus facilitating the indirect comparison of the competitive ability of their sperm through a common reference. The fraction of individuals fathered by the experimental and reference males is identified using markers, which allows one to estimate sperm competitive ability using simple mathematical expressions 7,8. In addition, sperm competitive ability can be estimated in two different scenarios depending on whether the experimental male is second or first to mate (offense and defense assay, respectively) 9, which is assumed to be reflective of different competence attributes. Here, we describe an approach that helps to interrogate the role of different genetic factors that putatively underlie the phenomenon of sperm competitive ability in D. melanogaster.
Developmental Biology, Issue 78, Molecular Biology, Cellular Biology, Genetics, Biochemistry, Spermatozoa, Drosophila melanogaster, Biological Evolution, Phenotype, genetics (animal and plant), animal biology, double-mating experiment, sperm competitive ability, male fertility, Drosophila, fruit fly, animal model
50547
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A Noninvasive Method For In situ Determination of Mating Success in Female American Lobsters (Homarus americanus)
Authors: Jason S Goldstein, Tracy L Pugh, Elizabeth A Dubofsky, Kari L Lavalli, Michael Clancy, Winsor H Watson III.
Institutions: University of New Hampshire, Massachusetts Division of Marine Fisheries, Boston University, Middle College.
Despite being one of the most productive fisheries in the Northwest Atlantic, much remains unknown about the natural reproductive dynamics of American lobsters. Recent work in exploited crustacean populations (crabs and lobsters) suggests that there are circumstances where mature females are unable to achieve their full reproductive potential due to sperm limitation. To examine this possibility in different regions of the American lobster fishery, a reliable and noninvasive method was developed for sampling large numbers of female lobsters at sea. This method involves inserting a blunt-tipped needle into the female's seminal receptacle to determine the presence or absence of a sperm plug and to withdraw a sample that can be examined for the presence of sperm. A series of control studies were conducted at the dock and in the laboratory to test the reliability of this technique. These efforts entailed sampling 294 female lobsters to confirm that the presence of a sperm plug was a reliable indicator of sperm within the receptacle and thus, mating. This paper details the methodology and the results obtained from a subset of the total females sampled. Of the 230 female lobsters sampled from George's Bank and Cape Ann, MA (size range = 71-145 mm in carapace length), 90.3% were positive for sperm. Potential explanations for the absence of sperm in some females include: immaturity (lack of physiological maturity), breakdown of the sperm plug after being used to fertilize a clutch of eggs, and lack of mating activity. The surveys indicate that this technique for examining the mating success of female lobsters is a reliable proxy that can be used in the field to document reproductive activity in natural populations.
Environmental Sciences, Issue 84, sperm limitation, spermatophore, lobster fishery, sex ratios, sperm receptacle, mating, American lobster, Homarus americanus
50498
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Collection and Cryopreservation of Hamster Oocytes and Mouse Embryos
Authors: Nuno Costa-Borges, Sheyla González, Elena Ibáñez, Josep Santaló.
Institutions: Universitat Autonoma de Barcelona.
Embryos and oocytes were first successfully cryopreserved more than 30 years ago, when Whittingham et al. 1 and Wilmut 2 separately described that mouse embryos could be frozen and stored at -196 °C and, a few years later, Parkening et al. 3 reported the birth of live offspring resulting from in vitro fertilization (IVF) of cryopreserved oocytes. Since then, the use of cryopreservation techniques has rapidly spread to become an essential component in the practice of human and animal assisted reproduction and in the conservation of animal genetic resources. Currently, there are two main methods used to cryopreserve oocytes and embryos: slow freezing and vitrification. A wide variety of approaches have been used to try to improve both techniques and millions of animals and thousands of children have been born from cryopreserved embryos. However, important shortcomings associated to cryopreservation still have to be overcome, since ice-crystal formation, solution effects and osmotic shock seem to cause several cryoinjuries in post-thawed oocytes and embryos. Slow freezing with programmable freezers has the advantage of using low concentrations of cryoprotectants, which are usually associated with chemical toxicity and osmotic shock, but their ability to avoid ice-crystal formation at low concentrations is limited. Slow freezing also induces supercooling effects that must be avoided using manual or automatic seeding 4. In the vitrification process, high concentrations of cryoprotectants inhibit the formation of ice-crystals and lead to the formation of a glasslike vitrified state in which water is solidified, but not expanded. However, due to the toxicity of cyroprotectants at the concentrations used, oocytes/embryos can only be exposed to the cryoprotectant solution for a very short period of time and in a minimum volume solution, before submerging the samples directly in liquid nitrogen 5. In the last decade, vitrification has become more popular because it is a very quick method in which no expensive equipment (programmable freezer) is required. However, slow freezing continues to be the most widely used method for oocyte/embryo cryopreservation. In this video-article we show, step-by-step, how to collect and slowly freeze hamster oocytes with high post-thaw survival rates. The same procedure can also be applied to successfully freeze and thaw mouse embryos at different stages of preimplantation development.
Developmental Biology, Issue 25, Cryopreservation, freezing, thawing, oocytes, embryos
1120
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A Method for Murine Islet Isolation and Subcapsular Kidney Transplantation
Authors: Erik J. Zmuda, Catherine A. Powell, Tsonwin Hai.
Institutions: The Ohio State University, The Ohio State University, The Ohio State University.
Since the early pioneering work of Ballinger and Reckard demonstrating that transplantation of islets of Langerhans into diabetic rodents could normalize their blood glucose levels, islet transplantation has been proposed to be a potential treatment for type 1 diabetes 1,2. More recently, advances in human islet transplantation have further strengthened this view 1,3. However, two major limitations prevent islet transplantation from being a widespread clinical reality: (a) the requirement for large numbers of islets per patient, which severely reduces the number of potential recipients, and (b) the need for heavy immunosuppression, which significantly affects the pediatric population of patients due to their vulnerability to long-term immunosuppression. Strategies that can overcome these limitations have the potential to enhance the therapeutic utility of islet transplantation. Islet transplantation under the mouse kidney capsule is a widely accepted model to investigate various strategies to improve islet transplantation. This experiment requires the isolation of high quality islets and implantation of islets to the diabetic recipients. Both procedures require surgical steps that can be better demonstrated by video than by text. Here, we document the detailed steps for these procedures by both video and written protocol. We also briefly discuss different transplantation models: syngeneic, allogeneic, syngeneic autoimmune, and allogeneic autoimmune.
Medicine, Issue 50, islet isolation, islet transplantation, diabetes, murine, pancreas
2096
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A Method for Ovarian Follicle Encapsulation and Culture in a Proteolytically Degradable 3 Dimensional System
Authors: Ariella Shikanov, Min Xu, Teresa K. Woodruff, Lonnie D. Shea.
Institutions: Northwestern University, Northwestern University, Feinberg School of Medicine, Northwestern University, Northwestern University, Northwestern University.
The ovarian follicle is the functional unit of the ovary that secretes sex hormones and supports oocyte maturation. In vitro follicle techniques provide a tool to model follicle development in order to investigate basic biology, and are further being developed as a technique to preserve fertility in the clinic1-4. Our in vitro culture system employs hydrogels in order to mimic the native ovarian environment by maintaining the 3D follicular architecture, cell-cell interactions and paracrine signaling that direct follicle development 5. Previously, follicles were successfully cultured in alginate, an inert algae-derived polysaccharide that undergoes gelation with calcium ions6-8. Alginate hydrogels formed at a concentration of 0.25% w/v were the most permissive for follicle culture, and retained the highest developmental competence 9. Alginate hydrogels are not degradable, thus an increase in the follicle diameter results in a compressive force on the follicle that can impact follicle growth10. We subsequently developed a culture system based on a fibrin-alginate interpenetrating network (FA-IPN), in which a mixture of fibrin and alginate are gelled simultaneously. This combination provides a dynamic mechanical environment because both components contribute to matrix rigidity initially; however, proteases secreted by the growing follicle degrade fibrin in the matrix leaving only alginate to provide support. With the IPN, the alginate content can be reduced below 0.25%, which is not possible with alginate alone 5. Thus, as the follicle expands, it will experience a reduced compressive force due to the reduced solids content. Herein, we describe an encapsulation method and an in vitro culture system for ovarian follicles within a FA-IPN. The dynamic mechanical environment mimics the natural ovarian environment in which small follicles reside in a rigid cortex and move to a more permissive medulla as they increase in size11. The degradable component may be particularly critical for clinical translation in order to support the greater than 106-fold increase in volume that human follicles normally undergo in vivo .
Bioengineering, Issue 49, Ovarian follicle, fibrin-alginate, 3D culture system, dynamic environment
2695
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Cryopreservation of Preimplantation Embryos of Cattle, Sheep, and Goats
Authors: Curtis R. Youngs.
Institutions: Iowa State University.
Preimplantation embryos from cattle, sheep, and goats may be cryopreserved for short- or long-term storage. Preimplantation embryos consist predominantly of water, and the avoidance of intracellular ice crystal formation during the cryopreservation process is of paramount importance to maintain embryo viability. Embryos are placed into a hypertonic solution (1.4 – 1.5 M) of a cryoprotective agent (CPA) such as ethylene glycol (EG) or glycerol (GLYC) to create an osmotic gradient that facilitates cellular dehydration. After embryos reach osmotic equilibrium in the CPA solution, they are individually loaded in the hypertonic CPA solution into 0.25 ml plastic straws for freezing. Embryos are placed into a controlled rate freezer at a temperature of -6°C. Ice crystal formation is induced in the CPA solution surrounding the embryo, and crystallization causes an increase in the concentration of CPA outside of the embryo, causing further cellular dehydration. Embryos are cooled at a rate of 0.5°C/min, enabling further dehydration, to a temperature of -34°C before being plunged into liquid nitrogen (-196°C). Cryopreserved embryos must be thawed prior to transfer to a recipient (surrogate) female. Straws containing the embryos are removed from the liquid nitrogen dewar, held in room temperature air for 3 to 5 sec, and placed into a 37°C water bath for 25 to 30 sec. Embryos cryopreserved in GLYC are placed into a 1 M solution of sucrose for 10 min for removal of the CPA before transfer to a recipient (surrogate) female. Embryos cryopreserved in EG, however, may be directly transferred to the uterus of a recipient.
Developmental Biology, Issue 54, embryo, cryopreservation, cattle, sheep, goats
2764
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Germ Cell Transplantation and Testis Tissue Xenografting in Mice
Authors: Lin Tang, Jose Rafael Rodriguez-Sosa, Ina Dobrinski.
Institutions: University of Calgary .
Germ cell transplantation was developed by Dr. Ralph Brinster and colleagues at the University of Pennsylvania in 19941,2. These ground-breaking studies showed that microinjection of germ cells from fertile donor mice into the seminiferous tubules of infertile recipient mice results in donor-derived spermatogenesis and sperm production by the recipient animal2. The use of donor males carrying the bacterial β-galactosidase gene allowed identification of donor-derived spermatogenesis and transmission of the donor haplotype to the offspring by recipient animals1. Surprisingly, after transplantation into the lumen of the seminiferous tubules, transplanted germ cells were able to move from the luminal compartment to the basement membrane where spermatogonia are located3. It is generally accepted that only SSCs are able to colonize the niche and re-establish spermatogenesis in the recipient testis. Therefore, germ cell transplantation provides a functional approach to study the stem cell niche in the testis and to characterize putative spermatogonial stem cells. To date, germ cell transplantation is used to elucidate basic stem cell biology, to produce transgenic animals through genetic manipulation of germ cells prior to transplantation4,5, to study Sertoli cell-germ cell interaction6,7, SSC homing and colonization3,8, as well as SSC self-renewal and differentiation9,10. Germ cell transplantation is also feasible in large species11. In these, the main applications are preservation of fertility, dissemination of elite genetics in animal populations, and generation of transgenic animals as the study of spermatogenesis and SSC biology with this technique is logistically more difficult and expensive than in rodents. Transplantation of germ cells from large species into the seminiferous tubules of mice results in colonization of donor cells and spermatogonial expansion, but not in their full differentiation presumably due to incompatibility of the recipient somatic cell compartment with the germ cells from phylogenetically distant species12. An alternative approach is transplantation of germ cells from large species together with their surrounding somatic compartment. We first reported in 2002, that small fragments of testis tissue from immature males transplanted under the dorsal skin of immunodeficient mice are able to survive and undergo full development with the production of fertilization competent sperm13. Since then testis tissue xenografting has been shown to be successful in many species and emerged as a valuable alternative to study testis development and spermatogenesis of large animals in mice14.
Developmental Biology, Issue 60, Spermatogonial stem cells (SSCs), germ cell transplantation, spermatogenesis, testis development, testis tissue xenografting
3545
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Use of Interferon-γ Enzyme-linked Immunospot Assay to Characterize Novel T-cell Epitopes of Human Papillomavirus
Authors: Xuelian Wang, William W. Greenfield, Hannah N. Coleman, Lindsey E. James, Mayumi Nakagawa.
Institutions: China Medical University , University of Arkansas for Medical Sciences , University of Arkansas for Medical Sciences .
A protocol has been developed to overcome the difficulties of isolating and characterizing rare T cells specific for pathogens, such as human papillomavirus (HPV), that cause localized infections. The steps involved are identifying region(s) of HPV proteins that contain T-cell epitope(s) from a subject, selecting for the peptide-specific T cells based on interferon-γ (IFN-γ) secretion, and growing and characterizing the T-cell clones (Fig. 1). Subject 1 was a patient who was recently diagnosed with a high-grade squamous intraepithelial lesion by biopsy and underwent loop electrical excision procedure for treatment on the day the T cells were collected1. A region within the human papillomavirus type 16 (HPV 16) E6 and E7 proteins which contained a T-cell epitope was identified using an IFN- g enzyme-linked immunospot (ELISPOT) assay performed with overlapping synthetic peptides (Fig. 2). The data from this assay were used not only to identify a region containing a T-cell epitope, but also to estimate the number of epitope specific T cells and to isolate them on the basis of IFN- γ secretion using commercially available magnetic beads (CD8 T-cell isolation kit, Miltenyi Biotec, Auburn CA). The selected IFN-γ secreting T cells were diluted and grown singly in the presence of an irradiated feeder cell mixture in order to support the growth of a single T-cell per well. These T-cell clones were screened using an IFN- γ ELISPOT assay in the presence of peptides covering the identified region and autologous Epstein-Barr virus transformed B-lymphoblastoid cells (LCLs, obtained how described by Walls and Crawford)2 in order to minimize the number of T-cell clone cells needed. Instead of using 1 x 105 cells per well typically used in ELISPOT assays1,3, 1,000 T-cell clone cells in the presence of 1 x 105 autologous LCLs were used, dramatically reducing the number of T-cell clone cells needed. The autologous LCLs served not only to present peptide antigens to the T-cell clone cells, but also to keep a high cell density in the wells allowing the epitope-specific T-cell clone cells to secrete IFN-γ. This assures successful performance of IFN-γ ELISPOT assay. Similarly, IFN- γ ELISPOT assays were utilized to characterize the minimal and optimal amino acid sequence of the CD8 T-cell epitope (HPV 16 E6 52-61 FAFRDLCIVY) and its HLA class I restriction element (B58). The IFN- γ ELISPOT assay was also performed using autologous LCLs infected with vaccinia virus expressing HPV 16 E6 or E7 protein. The result demonstrated that the E6 T-cell epitope was endogenously processed. The cross-recognition of homologous T-cell epitope of other high-risk HPV types was shown. This method can also be used to describe CD4 T-cell epitopes4.
Immunology, Issue 61, Interferon-γ enzyme-linked immunospot assay, T-cell, epitope, human papillomavirus
3657
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Polymerase Chain Reaction: Basic Protocol Plus Troubleshooting and Optimization Strategies
Authors: Todd C. Lorenz.
Institutions: University of California, Los Angeles .
In the biological sciences there have been technological advances that catapult the discipline into golden ages of discovery. For example, the field of microbiology was transformed with the advent of Anton van Leeuwenhoek's microscope, which allowed scientists to visualize prokaryotes for the first time. The development of the polymerase chain reaction (PCR) is one of those innovations that changed the course of molecular science with its impact spanning countless subdisciplines in biology. The theoretical process was outlined by Keppe and coworkers in 1971; however, it was another 14 years until the complete PCR procedure was described and experimentally applied by Kary Mullis while at Cetus Corporation in 1985. Automation and refinement of this technique progressed with the introduction of a thermal stable DNA polymerase from the bacterium Thermus aquaticus, consequently the name Taq DNA polymerase. PCR is a powerful amplification technique that can generate an ample supply of a specific segment of DNA (i.e., an amplicon) from only a small amount of starting material (i.e., DNA template or target sequence). While straightforward and generally trouble-free, there are pitfalls that complicate the reaction producing spurious results. When PCR fails it can lead to many non-specific DNA products of varying sizes that appear as a ladder or smear of bands on agarose gels. Sometimes no products form at all. Another potential problem occurs when mutations are unintentionally introduced in the amplicons, resulting in a heterogeneous population of PCR products. PCR failures can become frustrating unless patience and careful troubleshooting are employed to sort out and solve the problem(s). This protocol outlines the basic principles of PCR, provides a methodology that will result in amplification of most target sequences, and presents strategies for optimizing a reaction. By following this PCR guide, students should be able to: ● Set up reactions and thermal cycling conditions for a conventional PCR experiment ● Understand the function of various reaction components and their overall effect on a PCR experiment ● Design and optimize a PCR experiment for any DNA template ● Troubleshoot failed PCR experiments
Basic Protocols, Issue 63, PCR, optimization, primer design, melting temperature, Tm, troubleshooting, additives, enhancers, template DNA quantification, thermal cycler, molecular biology, genetics
3998
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High-throughput Screening for Small-molecule Modulators of Inward Rectifier Potassium Channels
Authors: Rene Raphemot, C. David Weaver, Jerod S. Denton.
Institutions: Vanderbilt University School of Medicine, Vanderbilt University School of Medicine, Vanderbilt University School of Medicine.
Specific members of the inward rectifier potassium (Kir) channel family are postulated drug targets for a variety of disorders, including hypertension, atrial fibrillation, and pain1,2. For the most part, however, progress toward understanding their therapeutic potential or even basic physiological functions has been slowed by the lack of good pharmacological tools. Indeed, the molecular pharmacology of the inward rectifier family has lagged far behind that of the S4 superfamily of voltage-gated potassium (Kv) channels, for which a number of nanomolar-affinity and highly selective peptide toxin modulators have been discovered3. The bee venom toxin tertiapin and its derivatives are potent inhibitors of Kir1.1 and Kir3 channels4,5, but peptides are of limited use therapeutically as well as experimentally due to their antigenic properties and poor bioavailability, metabolic stability and tissue penetrance. The development of potent and selective small-molecule probes with improved pharmacological properties will be a key to fully understanding the physiology and therapeutic potential of Kir channels. The Molecular Libraries Probes Production Center Network (MLPCN) supported by the National Institutes of Health (NIH) Common Fund has created opportunities for academic scientists to initiate probe discovery campaigns for molecular targets and signaling pathways in need of better pharmacology6. The MLPCN provides researchers access to industry-scale screening centers and medicinal chemistry and informatics support to develop small-molecule probes to elucidate the function of genes and gene networks. The critical step in gaining entry to the MLPCN is the development of a robust target- or pathway-specific assay that is amenable for high-throughput screening (HTS). Here, we describe how to develop a fluorescence-based thallium (Tl+) flux assay of Kir channel function for high-throughput compound screening7,8,9,10.The assay is based on the permeability of the K+ channel pore to the K+ congener Tl+. A commercially available fluorescent Tl+ reporter dye is used to detect transmembrane flux of Tl+ through the pore. There are at least three commercially available dyes that are suitable for Tl+ flux assays: BTC, FluoZin-2, and FluxOR7,8. This protocol describes assay development using FluoZin-2. Although originally developed and marketed as a zinc indicator, FluoZin-2 exhibits a robust and dose-dependent increase in fluorescence emission upon Tl+ binding. We began working with FluoZin-2 before FluxOR was available7,8 and have continued to do so9,10. However, the steps in assay development are essentially identical for all three dyes, and users should determine which dye is most appropriate for their specific needs. We also discuss the assay's performance benchmarks that must be reached to be considered for entry to the MLPCN. Since Tl+ readily permeates most K+ channels, the assay should be adaptable to most K+ channel targets.
Biochemistry, Issue 71, Molecular Biology, Chemistry, Cellular Biology, Chemical Biology, Pharmacology, Molecular Pharmacology, Potassium channels, drug discovery, drug screening, high throughput, small molecules, fluorescence, thallium flux, checkerboard analysis, DMSO, cell lines, screen, assay, assay development
4209
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Performing Vaginal Lavage, Crystal Violet Staining, and Vaginal Cytological Evaluation for Mouse Estrous Cycle Staging Identification
Authors: Ashleigh C. McLean, Nicolas Valenzuela, Stephen Fai, Steffany A.L. Bennett.
Institutions: Neural Regeneration Laboratory and Ottawa Institute of Systems Biology, University of Ottawa , University of Ottawa , Azrieli School of Architecture and Urbanism.
A rapid means of assessing reproductive status in rodents is useful not only in the study of reproductive dysfunction but is also required for the production of new mouse models of disease and investigations into the hormonal regulation of tissue degeneration (or regeneration) following pathological challenge. The murine reproductive (or estrous) cycle is divided into 4 stages: proestrus, estrus, metestrus, and diestrus. Defined fluctuations in circulating levels of the ovarian steroids 17-β-estradiol and progesterone, the gonadotropins luteinizing and follicle stimulating hormones, and the luteotropic hormone prolactin signal transition through these reproductive stages. Changes in cell typology within the murine vaginal canal reflect these underlying endocrine events. Daily assessment of the relative ratio of nucleated epithelial cells, cornified squamous epithelial cells, and leukocytes present in vaginal smears can be used to identify murine estrous stages. The degree of invasiveness, however, employed in collecting these samples can alter reproductive status and elicit an inflammatory response that can confound cytological assessment of smears. Here, we describe a simple, non-invasive protocol that can be used to determine the stage of the estrous cycle of a female mouse without altering her reproductive cycle. We detail how to differentiate between the four stages of the estrous cycle by collection and analysis of predominant cell typology in vaginal smears and we show how these changes can be interpreted with respect to endocrine status.
Medicine, Issue 67, Biochemistry, Immunology, Microbiology, Physiology, Anatomy, estrous cycle, vaginal cytology, hormonal status, murine reproduction, 17-beta-estradiol, progesterone, luteinizing hormone, follicle-stimulating hormone, prolactin
4389
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Dual Somatic Recordings from Gonadotropin-Releasing Hormone (GnRH) Neurons Identified by Green Fluorescent Protein (GFP) in Hypothalamic Slices
Authors: Peter J. Hemond, Kelly J. Suter.
Institutions: University of Texas San Antonio - UTSA.
Gonadotropin-Releasing Hormone (GnRH) is a small neuropeptide that regulates pituitary release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These gonadotropins are essential for the regulation of reproductive function. The GnRH-containing neurons are distributed diffusely throughout the hypothalamus and project to the median eminence where they release GnRH from their axon terminals into the hypophysiotropic portal system (1). In the portal capillaries, GnRH travels to the anterior pituitary gland to stimulate release of gonadotropins into systemic circulation. GnRH release is not continuous but rather occurs in episodic pulses. It is well established that the intermittent manner of GnRH release is essential for reproduction (2, 3). Coordination of activity of multiple GnRH neurons probably underlies GnRH pulses. Total peptide content in GnRH neurons is approximately 1.0 pg/cell (4), of which 30% likely comprises the releasable pool. Levels of GnRH during a pulse (5, 6), suggest multiple GnRH neurons are probably involved in neurosecretion. Likewise, single unit activity extracted from hypothalamic multi-unit recordings during LH release indicates changes in activity of multiple neurons (7). The electrodes with recorded activity during LH pulses are associated with either GnRH somata or fibers (8). Therefore, at least some of this activity arises from GnRH neurons. The mechanisms that result in synchronized firing in hypothalamic GnRH neurons are unknown. Elucidating the mechanisms that coordinate firing in GnRH neurons is a complex problem. First, the GnRH neurons are relatively few in number. In rodents, there are 800-2500 GnRH neurons. It is not clear that all GnRH neurons are involved in episodic GnRH release. Moreover, GnRH neurons are diffusely distributed (1). This has complicated our understanding of coordination of firing and has made many technical approaches intractable. We have optimized loose cell-attached recordings in current-clamp mode for the direct detection of action potentials and developed a recording approach that allows for simultaneous recordings from pairs of GnRH neurons.
Jove Neuroscience, Issue 36, electrophysiology, simultaneous recording, cell-attached recording, current clamp, brain slice
1678
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Gibberella zeae Ascospore Production and Collection for Microarray Experiments.
Authors: Matias Pasquali, Corby Kistler.
Institutions: USDA, University of Minnesota/ Agroinnova, University of Torino, University of Minnesota.
Fusarium graminearum Schwabe (teleomorph Gibberella zeae) is a plant pathogen causing scab disease on wheat and barley that reduces crop yield and grain quality. F. graminearum also causes stalk and ear rots of maize and is a producer of mycotoxins such as the trichothecenes that contaminate grain and are harmful to humans and livestock (Goswami and Kistler, 2004). The fungus produces two types of spores. Ascospores, the propagules resulting from sexual reproduction, are the main source of primary infection. These spores are forcibly discharged from mature perithecia and dispersed by wind (Francl et al 1999). Secondary infections are mainly caused by macroconidia which are produced by asexual means on the plant surface. To study the developmental processes of ascospores in this fungus, a procedure for their collection in large quantity under sterile conditions was required. Our protocol was filmed in order to generate the highest level of information for understanding and reproducibility; crucial aspects when full genome gene expression profiles are generated and interpreted. In particular, the variability of ascospore germination and biological activity are dependent on the prior manipulation of the material. The use of video for documenting every step in ascospore production is proposed in order to increase standardization, complying with the increasingly stringent requirements for microarray analysis. The procedure requires only standard laboratory equipment. Steps are shown to prevent contamination and favor time synchronization of ascospores.
Plant Biology, Issue 1, sexual cross, spore separation, MIAME standards
115
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