JoVE Bioengineering
Fabrication of Micro-tissues using Modules of Collagen Gel Containing Cells
1Institute of Biomaterials and Biomedical Engineering / Department of Chemical Engineering and Applied Chemistry, University of Toronto, 2Institute of Biomaterials and Biomedical Engineering, University of Toronto
Creation of micro-tissues using cylindrical collagen gels, called modules, that contain embedded cells and which surface is coated with endothelial cells.
JoVE Bioengineering
A Method for Ovarian Follicle Encapsulation and Culture in a Proteolytically Degradable 3 Dimensional System
1Institute for BioNanotechnology in Advanced Medicine, Northwestern University, 2Department of Obstetrics and Gynecology, Northwestern University, Feinberg School of Medicine, 3Center for Reproductive Research, Northwestern University, 4The Robert H. Lurie Comprehensive Cancer Center, Northwestern University, 5Department of Chemical and Biological Engineering, Northwestern University
A new method for ovarian follicle encapsulation in a 3D fibrin-alginate interpenetrating network is described. This system combines structural support with proteolytic degradation to support the development of immature follicles to produce mature oocytes. This method may be applied to culture cell aggregates to maintain cell-cell contacts without limiting expansion.
JoVE Neuroscience
Isolation of Cerebrospinal Fluid from Rodent Embryos for use with Dissected Cerebral Cortical Explants
1Department of Physical Medicine and Rehabilitation, VA Greater Los Angeles Healthcare System, 2Department of Pharmacology and Physiology, Institute for Neuroscience, The George Washington University School of Medicine and Health Sciences, 3Division of Genetics, Department of Medicine, Boston Children's Hospital, 4Howard Hughes Medical Institute, Boston Children's Hospital, 5Department of Pathology, Boston Children's Hospital, Harvard Medical School
The ventricular cerebrospinal fluid (CSF) bathes the neuroepithelial and cerebral cortical progenitor cells during early brain development in the embryo. Here we describe the method developed to isolate ventricular CSF from rodent embryos of different ages in order to investigate its biological function. In addition, we demonstrate our cerebral cortical explant dissection and culture technique that allows for explant growth with minimal volumes of culture medium or CSF.
JoVE General
Functional Imaging of Brown Fat in Mice with 18F-FDG micro-PET/CT
1Department of Translational Imaging, The Methodist Hospital Research Institute, Houston, 2Diabetes Research Center, The Methodist Hospital Research Institute, Houston
A method of functional imaging of mouse brown adipose tissue (BAT) is described in which cold-stimulated uptake of 18F-Fluorodeoxyglucose (FDG) in BAT is non-invasively assessed with a standardized micro-PET/CT protocol. This method is robust and sensitive to detect differences in BAT activities in mouse models.
JoVE Neuroscience
Intact Histological Characterization of Brain-implanted Microdevices and Surrounding Tissue
1Weldon School of Biomedical Engineering, Purdue University, 2Department of Biological Sciences, Purdue University
Here we present a histological method for capturing, labeling, optically clearing, and imaging the intact brain tissue interface around chronically implanted microdevices in rodent brain tissue. Results from the techniques comprising this method are useful for understanding the impact of various penetrating brain-implants on their surrounding tissue.
JoVE General
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
We present two processes for the microfabrication of porous polymer chips for three-dimensional cell cultivation. The first one is hot embossing combined with a solvent vapour welding process. The second one uses a recently developed microthermoforming process combined with ion track technology leading to a significant simplification of manufacture.
JoVE Clinical and Translational Medicine
Orthotopic Small Bowel Transplantation in Rats
1Department of Surgery, University of Bonn, Germany, 2Department of Surgery, Kyoto University Hospital
Small bowel transplantation has become an accepted treatment option for patients with irreversible intestinal failure. Our experimental model of orthotopic small bowel transplantation in rats serves as a reliable tool to address underlying immunologic and inflammatory processes that complicate intestinal transplantation.
JoVE Clinical and Translational Medicine
Controlled Cervical Laceration Injury in Mice
1Norton Neuroscience Institute, Norton Healthcare, 2Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Department of Neurological Surgery and Goodman and Campbell Brain and Spine, Medical Neuroscience Graduate Program, and Department of Anatomy and Cell Biology, Indiana University School of Medicine
A novel technique to create a reproducible in vivo model of cervical spinal cord laceration injury in the mouse is described. This technique is based on spine stabilization by fixation of the cervical facets and laceration of the spinal cord using an oscillating blade with an accuracy of ±0.01 mm.
JoVE General
Non-radioactive in situ Hybridization Protocol Applicable for Norway Spruce and a Range of Plant Species
1Department of Evolutionary Functional Genomics, Evolutionary Biology Center, Uppsala University, 2Department of Plant Biology and Forest Genetics, Uppsala BioCenter, Swedish University of Agricultural Sciences
We describe a modified DIG in situ hybridization protocol, which is fast and applicable on a wide range of plant species including Norway spruce. With just a few adjustments, including altered RNase treatment and proteinase K concentration, the protocol may be used in studies of different tissues and species.
JoVE General
Micro-dissection of Rat Brain for RNA or Protein Extraction from Specific Brain Region
Micro-dissection of rat brain into various regions is extremely important for the study of different neurodegenerative diseases. This video demonstrates micro-dissection of four major brain regions include olfactory bulb, frontal cortex, striatum and hippocampus in fresh rat brain tissue. Useful tips for quick removal of respective regions to avoid RNA and protein degradation of the tissue are given.
JoVE Clinical and Translational Medicine
Segmentation and Measurement of Fat Volumes in Murine Obesity Models Using X-ray Computed Tomography
1Carestream Molecular Imaging, 2Department of Chemistry and Biochemistry, University of Notre Dame, 3Freimann Life Science Center, University of Notre Dame, 4Research and Development, Oncovision, GEM-Imaging S.A.
Fat content analysis is routinely conducted in studies utilizing murine obesity models. Emerging methods in small animal CT imaging and analysis are providing for longitudinal detail rich fat content analysis. Here we detail step by step procedures for performing small animal CT imaging, analysis, and visualization.
JoVE General
Adult and Embryonic Skeletal Muscle Microexplant Culture and Isolation of Skeletal Muscle Stem Cells
School of Biosciences, University of Birmingham
The micro-dissected explants technique is a robust and reliable method for isolating proliferative skeletal muscle cells from juvenile, adult or embryonic muscles as a source of skeletal muscle stem cells. Uniquely, these cells have been clonally derived to produce skeletal muscle stem cell lines used for in vivo transplantation.
JoVE General
Chip-based Three-dimensional Cell Culture in Perfused Micro-bioreactors
Institute for Biological Interfaces, Forschungszentrum Karlsruhe
We describe a chip-based platform for the three-dimensional cultivation of cells in micro-bioreactors. One chip can house up to 10 Mio. cells that can be cultivated under precisely defined conditions with regard to fluid flow, oxygen tension etc. in a sterile, closed circulation loop.
JoVE Neuroscience
Cerebrovascular Casting of the Adult Mouse for 3D Imaging and Morphological Analysis
1Center for Cerebrovascular Research, Department of Anesthesia and Perioperative Care, University of California, San Francisco, 2Department of Neurological Surgery, University of California, San Francisco, 3Department of Neurology, University of California, San Francisco
In this article, we present a simple, practical technique for cerebrovascular casting that is easy to perform and can be utilized to image the vascular tree of the adult mouse brain.
JoVE General
A Chromatin Assay for Human Brain Tissue
Psychiatry, Brudnick Neuropsychiatric Research Institute, University of Massachusetts Medical School
Until recently, expression studies on human brain were limited to quantification of RNA or protein. With the chromatin immunoprecipitation techniques described in this paper, it will be possible to map histone methylation and other epigenetic regulators of gene expression in postmortem brain.
JoVE Clinical and Translational Medicine
Improved Visualization of Lung Metastases at Single Cell Resolution in Mice by Combined In-situ Perfusion of Lung Tissue and X-Gal Staining of lacZ-Tagged Tumor Cells
Laboratory for Orthopedic Research, Balgrist University Hospital, Zurich
The novel protocol reported in the present study allows selective detection of lung metastases at single cell resolution in mice by combined in-situ lung perfusion and fixation and X-Gal staining of lacZ-tagged tumor cells.
JoVE General
A Neuronal and Astrocyte Co-Culture Assay for High Content Analysis of Neurotoxicity
Bioscience Division, High Content Analysis Research and Development, Millipore Inc
This article describes a novel protocol and reagent set designed for sensitive measurement of neurotoxic effects of compounds and treatments on co-cultures of neurons and astrocytes using high content analysis. Results demonstrate that high content analysis represents an exciting novel technology for neurotoxicity assessment.
JoVE Clinical and Translational Medicine
A Simplified Technique for Producing an Ischemic Wound Model
Department of Surgery, University of Louisville
We have developed a minimally invasive technique to create a rabbit ischemic ear wound model by dividing the central artery and nerve and the cranial neurovascular bundle. A subcutaneous tunnel then cuts all subcutaneous tissues. This procedure causes minimal skin disruption and can be safely used in diabetic animals.
JoVE Clinical and Translational Medicine
Murine Fetal Echocardiography
Fetal and perinatal death is a common feature when studying genetic alterations affecting cardiac development. High-frequency ultrasound imaging has improved 2-D resolution and can provide excellent information on early cardiac development and is an ideal method to detect the impact on cardiac structure and function prior to death.
JoVE Neuroscience
Voltage Biasing, Cyclic Voltammetry, & Electrical Impedance Spectroscopy for Neural Interfaces
1Weldon School of Biomedical Engineering, Purdue University, 2Biomedical Engineering, University of Wisconsin-Madison, 3Biomedical Engineering, University of Michigan, 4Department of Biological Sciences, Purdue University
The electrode-tissue interface of neural recording electrodes can be characterized with electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Application of voltage biasing changes the electrochemical properties of the electrode-tissue interface and can improve recording capability. Voltage biasing, EIS, CV, and neural recordings are complementary.
JoVE Clinical and Translational Medicine
Non-invasive Imaging of Acute Allograft Rejection after Rat Renal Transplantation Using 18F-FDG PET
1Department of Internal Medicine D, Experimental Nephrology, University of Münster, 2Department of Nuclear Medicine, University of Münster, 3European Institute for Molecular Imaging, University of Münster
We herein present a rat renal transplantation model to non-invasively assess acute allograft rejection using positron emission tomography with 18F-fluorodeoxyglucose.
JoVE Neuroscience
Targeted Labeling of Neurons in a Specific Functional Micro-domain of the Neocortex by Combining Intrinsic Signal and Two-photon Imaging
Department of Neuroscience, Medical University of South Carolina
A method is described for labeling neurons with fluorescent dyes in predetermined functional micro-domains of the neocortex. First, intrinsic signal optical imaging is used to obtain a functional map. Then two-photon microscopy is used to label and image neurons within a micro-domain of the map.
JoVE Clinical and Translational Medicine
Patient Derived Cell Culture and Isolation of CD133+ Putative Cancer Stem Cells from Melanoma
1Institute of Pathology, Laboratory of Molecular Tumor Pathology, Charité - Universitätsmedizin Berlin, 2Institute for Chemistry and Biochemistry, Free University Berlin, 3Laboratory for Functional Genomics Charité (LFGC), Charité - Universitätsmedizin Berlin, 4Comprehensive Cancer Center Charité, Charité - Universitätsmedizin Berlin
This article describes the preparation of freshly obtained melanoma tissue into primary cell cultures, and how to remove contaminations of erythrocytes and fibroblasts from the tumor cells. Finally, we describe how CD133+ putative melanoma stem cells are sorted from the CD133- bulk using Magnetic Activated Cell Sorting (MACS).
JoVE General
Laser Capture Microdissection of Mammalian Tissue
Department of Pathology, University of California, Irvine (UCI)
JoVE Clinical and Translational Medicine
Roux-en-Y Gastric Bypass Operation in Rats
1Department of Surgery, University Hospital Zürich, 2Zürich Centre for Integrative Human Physiology, University of Zürich, 3Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zürich, 4Imperial Weight Centre, Department of Investigative Medicine, Imperial College London
Numerous studies using gastric bypass rat models have been recently conducted to uncover the underlying physiological mechanisms of Roux-en-Y gastric bypass operations. This article aims to demonstrate and discuss the technical and experimental details of our published gastric bypass rat model to understand advantages and limitations of this experimental tool.
JoVE Bioengineering
High Resolution 3D Imaging of Ex-Vivo Biological Samples by Micro CT
1Department of Molecular Genetics, Weizmann Institute of Science, 2Department of Biological Regulation, Weizmann Institute of Science, 3Department of Chemical Infrastructure, Weizmann Institute of Science
Non-destructive volume visualization can be achieved only by tomographic techniques, of which the most efficient is the x-ray micro computerized tomography ( CT).
JoVE Neuroscience
Chromatin Immunoprecipitation from Dorsal Root Ganglia Tissue following Axonal Injury
1Laboratory for NeuroRegeneration and Repair, Department of Neurology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 2Graduate School for Cellular and Molecular Neuroscience, University of Tuebingen
We present a method for chromatin immunoprecipitation from dorsal root ganglia tissue following axonal injury. The approach can be used to identify specific transcription factor binding sites and epigenetic modification of histone and DNA important for the regeneration of injured axons in both the peripheral and central nervous system.
JoVE Bioengineering
Postproduction Processing of Electrospun Fibres for Tissue Engineering
1Materials Science and Engineering, University of Sheffield, 2Department of Biomedical Science, University of Sheffield, 3Department of Chemistry, University of Sheffield
Electrospun scaffolds can be processed post production for tissue engineering applications. Here we describe methods for spinning complex scaffolds (by consecutive spinning), for making thicker scaffolds (by multi-layering using heat or vapour annealing), for achieving sterility (aseptic production or sterilisation post production) and for achieving appropriate biomechanical properties.
JoVE General
Electrospinning Fibrous Polymer Scaffolds for Tissue Engineering and Cell Culture
Department of Bioengineering, University of Pennsylvania
The process of electrospinning polymers for tissue engineering and cell culture is addressed in this article. Specifically, the electrospinning of photoreactive macromers with additional processing capabilities of photopatterning and multi-polymer electrospinning is described.
JoVE General
Using High Resolution Computed Tomography to Visualize the Three Dimensional Structure and Function of Plant Vasculature
1U.S. Department of Agriculture, 2Department of Viticulture and Enology, University of California - Davis, 3Hawkesbury Institute for the Environment, University of Western Sydney, 4Advanced Light Source, Lawrence Berkeley National Lab, 5Citrus Research & Education Center, University of Florida
High resolution x-ray computed tomography (HRCT) is a non-destructive diagnostic imaging technique that can be used to study the structure and function of plant vasculature in 3D. We demonstrate how HRCT facilitates exploration of xylem networks across a wide range of plant tissues and species.
JoVE General
Primary Culture and Plasmid Electroporation of the Murine Organ of Corti.
1Department of Otology and Laryngology, Harvard Medical School, 2Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 3Department of Communication Sciences and Disorders, Emerson College, 4Program in Speech and Hearing Bioscience and Technology, Division of Health Science and Technology, Harvard
This procedure describes a method for the isolation and culture of the murine organ of Corti with or without the spiral limbus and spiral ganglion neurons. We also demonstrate a method for the expression of an exogenous reporter gene in the organ of Corti explant by electroporation.
JoVE Bioengineering
Microfabricated Platforms for Mechanically Dynamic Cell Culture
1Department of Mechanical and Industrial Engineering, University of Toronto, 2Institute of Biomaterials and Biomedical Engineering, University of Toronto, 3Faculty of Dentistry, University of Toronto
In this protocol, we demonstrate the fabrication of a microactuator array of vertically displaced posts on which the technology is based, and how this base technology can be modified to conduct high-throughput mechanically dynamic cell culture in both two-dimensional and three-dimensional culture paradigms.
JoVE Bioengineering
Electrospinning Fundamentals: Optimizing Solution and Apparatus Parameters
1Department of Biomedical Engineering, University of Michigan, 2State Key Laboratory of Bioelectronics, Southeast University, 3Department of Neurology, University of Michigan, 4Geriatrics Research, Education and Clinical Center, Veterans Affairs Ann Arbor Healthcare Center
Electrospinning techniques can create a variety of nanofibrous scaffolds for tissue engineering or other applications. We describe here a procedure to optimize the parameters of the electrospinning solution and apparatus to obtain fibers with the desired morphology and alignment. Common problems and troubleshooting techniques are also presented.
JoVE General
A Noninvasive Hair Sampling Technique to Obtain High Quality DNA from Elusive Small Mammals
We present a noninvasive sampling approach to efficiently collect hair samples from elusive small mammals, as shown for the American pika. We demonstrate the utility of this method by extracting DNA from sampled hair and amplifying several types of molecular markers commonly used in studies of wildlife ecology and conservation.
JoVE Neuroscience
Large-scale Recording of Neurons by Movable Silicon Probes in Behaving Rodents
1Center for Molecular and Behavioral Neuroscience, University of New Jersey, 2Center for Interdisciplinary Research in Biology, Collège de France, 3Janelia Farm Research Campus, Howards Hughes Medical Institute, 4Deptartment of Psychology, University of Wisconsin at Milwaukee
We describe methods for large-scale recording of multiple single units and local field potential in behaving rodents with silicon probes. Drive fabrication, probe attachment to the drive and probe implantation processes are illustrated in sufficient details for easy replication.
JoVE Clinical and Translational Medicine
Induction of Myocardial Infarction in Adult Zebrafish Using Cryoinjury
Department of Biology, Unit of Zoology, University of Fribourg, Fribourg, Switzerland
Zebrafish represents a valuable model to study the mechanisms of heart regeneration in vertebrates. Here, we present a protocol for induction of a heart infarct in adult zebrafish using cryoinjury. This method results in massive cell death within 20% of the ventricular wall, similar to that observed in mammalian infarcts.
JoVE Immunology and Infection
Infection of Zebrafish Embryos with Intracellular Bacterial Pathogens
1Department of Molecular Cell Biology, Institute of Biology, Leiden University, 2Department of Medical Microbiology and Infection Control, VU University Medical Center, 3Australian Regenerative Medicine Institute, Monash University
Transparent zebrafish embryos have proved useful model hosts to visualize and functionally study interactions between innate immune cells and intracellular bacterial pathogens, such as Salmonella typhimurium and Mycobacterium marinum. Micro-injection of bacteria and multi-color fluorescence imaging are essential techniques involved in the application of zebrafish embryo infection models.
JoVE Immunology and Infection
Monitoring Dendritic Cell Migration using 19F / 1H Magnetic Resonance Imaging
1Experimental and Clinical Research Center, A joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine, 2Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrück Center for Molecular Medicine
Tracking of cells using MRI has gained remarkable attention in the past years. This protocol describes the labeling of dendritic cells with fluorine (19F)-rich particles, the in vivo application of these cells, and monitoring the extent of their migration to the draining lymph node with 19F/1H MRI and 19F MRS.
JoVE General
Chromatin Immunoprecipitation from Human Embryonic Stem Cells
Department of Biochemistry, University of California - Riverside
The differentiation of ESC coincides with cell-type specific changes in the structure and composition of chromatin. The detection of those changes provides valuable insights into the mechanisms that define stemcellness and cell differentiation. Chromatin immunoprecipitation (ChIP) represents a valuable method to dissect the molecular mechanisms underlying stem cell differentiation.
JoVE General
Visualizing the Beating Heart in Drosophila
Development and Aging Program, The Sanford Burnham Institute for Medical Research
Technique required for visualizing the beating heart in larval and adult Drosophila are presented. Each life stage requires a different methodology.
JoVE Clinical and Translational Medicine
Contrast Enhanced Vessel Imaging using MicroCT
1Greehey Children's Cancer Research Institute, University of Texas Health Science Center at San Antonio, 2Small Animal Imaging Resources facility, University of Texas Health Science Center at San Antonio, 3Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, 4Department of Pediatrics, University of Texas Health Science Center at San Antonio
Contrast enhanced small animal vessel imaging by microCT is a rapid, cost-effective and high-throughput technique for serial in situ examination for tumor development, for analyzing the network of blood vessels that nourish them, and for following the response of tumors to preclinical therapeutic intervention(s).
JoVE General
Neuronal Nuclei Isolation from Human Postmortem Brain Tissue
Psychiatry, Brudnick Neuropsychiatric Research Institute, University of Massachusetts Medical School
The cellular heterogeneity of brain tissue poses a significant limitation for the study of epigenetic markings in chromatin because most assays lack single cell resolution. Neurons typically are intermingled with glia and other non-neuronal cells. We provide a protocol to extract and collect neuronal nuclei from human brain.
JoVE General
Studying Membrane Biogenesis with a Luciferase-Based Reporter Gene Assay
1Department of Molecular and Cell Biology, Harvard, 2Molecular and Metabolic Signalling Centre, Division of Basic Medical Sciences, St. George's University of London
Here, we describe procedures for studying changes in phagocytosis-induced gene expression with a luciferase-based reporter gene approach using the Dual-GloTM Luciferase Assay System from Promega.
JoVE Bioengineering
Fabrication of Micropatterned Hydrogels for Neural Culture Systems using Dynamic Mask Projection Photolithography
Biomedical Engineering, Tulane University
Simple techniques are described for the rapid production of microfabricated neural culture systems using a digital micromirror device for dynamic mask projection lithography on regular cell culture substrates. These culture systems may be more representative of natural biological architecture, and the techniques described could be adapted for numerous applications.
JoVE Immunology and Infection
Tracking Neutrophil Intraluminal Crawling, Transendothelial Migration and Chemotaxis in Tissue by Intravital Video Microscopy
Department of Pharmacology, University of Saskatchewan
We describe a protocol of brightfield intravital microscopy for measuring dynamic neutrophil-endothelial cell interactions during neutrophil recruitment in response to the source of a neutrophil chemoattractant in vivo. Neutrophil intraluminal crawling, transendothelial migration and chemotaxis in mouse cremaster muscle tissue are visualized with time-lapsed video photography and tracked with ImageJ.
JoVE General
Non-plasma Bonding of PDMS for Inexpensive Fabrication of Microfluidic Devices
1Department of Biomedical Engineering, University of California, Irvine (UCI), 2Stem Cell Research Center, University of California, Irvine (UCI), 3Institute for Brain Aging and Dementia, University of California, Irvine (UCI)
In this video we demonstrate how to use the neuron microfluidic device without plasma bonding.
JoVE General
Micro-Mechanical Characterization of Lung Tissue Using Atomic Force Microscopy
The stiffness of the extracellular matrix strongly influences multiple behaviors of adherent cells. Matrix stiffness varies spatially throughout a tissue, and undergoes modification in various disease conditions. Here we develop methods to characterize spatial variations in stiffness in normal and fibrotic mouse lung tissue using atomic force microscopy microindentation.
JoVE General
Assessment of Mitochondrial Functions and Cell Viability in Renal Cells Overexpressing Protein Kinase C Isozymes
The effects of activation of protein kinase C (PKC) isozymes on mitochondrial functions associated with respiration and oxidative phosphorylation and on cell viability are described. The approach adapts adenoviral technique to selectively overexpress PKC isozymes in primary cell culture and a variety of assays to determine mitochondrial functions and energy status of the cell.
JoVE General
Immunocytochemistry: Human Neural Stem Cells
Department of Pathology, University of California, Irvine (UCI)
Immunocytochemistry is a powerful method to determine the presence, subcellular localization, and relative abundance of an antigen of interest in cultured cells. This protocol presents an easy-to-follow series of steps that will enable one to conserve antibodies and get the most out of one's staining.
JoVE General
Preparation of Dissociated Mouse Cortical Neuron Cultures
Department of Anatomy and Neurobiology, University of California, Irvine (UCI)
This video shows a procedure for generating neuronal cultures from late embryo and early postnatal mouse cortex. These cultures can be used for immunocytochemistry, biochemistry, electrophysiology, calcium and sodium imaging and provide a platform to study the neuronal development of transgenic animals that carry a postnatal lethal gene mutation.
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