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Extracellular Fluid: The fluid of the body that is outside of Cells. It is the external environment for the cells.

Tonicity in Animals

JoVE 10702

The tonicity of a solution determines if a cell gains or loses water in that solution. The tonicity depends on the permeability of the cell membrane for different solutes and the concentration of nonpenetrating solutes in the solution within and outside of the cell. If a semipermeable membrane hinders the passage of some solutes but allows water to follow its concentration gradient, water moves from the side with low osmolarity (i.e., less solute) to the side with higher osmolarity (i.e., higher solute concentration). Tonicity of the extracellular fluid determines the magnitude and direction of osmosis and results in three possible conditions: hypertonicity, hypotonicity, and isotonicity. In biology, the prefix “iso” means equal or being of equal measurements. When extracellular and intracellular fluid have an equal concentration of nonpenetrating solute inside and outside, the solution is isotonic. Isotonic solutions have no net movement of water. Water will still move in and out, just in equal proportions. Therefore, no change in cell volume occurs. The prefix “hypo” means lower or below. Whenever there is a low concentration of nonpenetrating solute and a high concentration of water outside relative to inside, the environment is hypotonic. Water will move into the cell, causing it to swell. In animal cells, the swelling ul

 Core: Membranes and Cellular Transport

What is the Endocrine System?

JoVE 10875

The endocrine system sends hormones—chemical signals—through the bloodstream to target cells—the cells the hormones selectively affect. These signals are produced in endocrine cells, secreted into the extracellular fluid, and then diffuse into the blood. Eventually, they diffuse out of the blood and bind to target cells which have specialized receptors to recognize the hormones. While most hormones travel through the circulatory system to reach their target cells, there are also alternate routes to bring hormones to target cells. Paracrine signaling sends hormones out of the endocrine cell and into the extracellular fluid where they affect local cells. In a form of paracrine signaling, called autocrine signaling, hormones secreted into the extracellular fluid affect the cell that secreted them. Another type of signaling, synaptic signaling, involves the release of neurotransmitters from neuron terminals into the synapse—a specialized junction that relays information between neurons—where they bind to receptors on neighboring neurons, muscle cells, and glands. In neuroendocrine signaling, neurosecretory cells secrete neurohormones that travel through the blood to affect target cells. Overall, endocrine signaling has a slower effect than other types of signaling because it takes longer for hormones to reach the target cel

 Core: Endocrine System


JoVE 10709

Cells use energy-requiring bulk transport mechanisms to transfer large particles, or large amounts of small particles, into or out of the cell. The cells envelop the particles in spherical membranes called vesicles or vacuoles. Vesicles that transport material into the cell are built from the cell membrane. These vesicles encapsulate external molecules and transport them into the cell in a process called endocytosis. Pinocytosis (“cellular drinking”) is one of three main types of endocytosis. In pinocytosis, the cell repeatedly takes in fluid from the surrounding environment using tiny vesicles. Pinocytosis occurs in many cell types. In the small intestine, bristle-like protrusions called microvilli use pinocytosis to absorb nutrients from food. Egg cells use pinocytosis to obtain nutrients before fertilization. In pinocytosis and other forms of endocytosis, vesicles form when sections of the cell membrane sink inward, creating tear-shaped pockets that surround the material being taken into the cell. In pinocytosis, the imported material consists of fluid and other molecules. As the membrane reconnects, the vesicles pinch off, separating from the membrane. In the process, the vesicles enter the cell, taking the enclosed substances with them. Specific characteristics distinguish pinocytosis from the other forms of endocytosis&mdash

 Core: Membranes and Cellular Transport

Lymph Node Exam

JoVE 10061

Source: Richard Glickman-Simon, MD, Assistant Professor, Department of Public Health and Community Medicine, Tufts University School of Medicine, MA

The lymphatic system has two main functions: to return extracellular fluid back to the venous circulation and to expose antigenic substances to the immune system. As the collected fluid passes …

 Physical Examinations II

Protein Associations

JoVE 10704

The cell membrane—or plasma membrane—is an ever-changing landscape. It is described as a fluid mosaic as various macromolecules are embedded in the phospholipid bilayer. Among the macromolecules are proteins. The protein content varies across cell types. For example, mitochondrial inner membranes contain ~76%, while myelin contains ~18% protein content. Individual cells contain many types ofbrane proteins—red blood cells contain over 50—and different cell types harbor distinct membrane protein sets. Membrane proteins have wide-ranging functions. For example, they can be channels or carriers that transport substances, enzymes with metabolic roles, or receptors that bind to chemical messengers. Like membrane lipids, most membrane proteins contain hydrophilic (water-loving) and hydrophobic (water-fearing) regions. The hydrophilic areas are exposed to water-containing solution inside the cell, outside the cell, or both. The hydrophobic regions face the hydrophobic tails of phospholipids within the membrane bilayer. Membrane proteins can be classified by whether they are embedded (integral) or associated with the cell membrane (peripheral). Most integral proteins are transmembrane proteins, which traverse both phospholipid layers, spanning the entire membrane. Their hydrophilic regions extend from both sides of the membrane, facing cytosol on

 Core: Membranes and Cellular Transport

The Resting Membrane Potential

JoVE 10845

The relative difference in electrical charge, or voltage, between the inside and the outside of a cell membrane, is called the membrane potential. It is generated by differences in permeability of the membrane to various ions and the concentrations of these ions across the membrane.

The membrane potential of a cell can be measured by inserting a microelectrode into a cell and comparing the charge to a reference electrode in the extracellular fluid. The membrane potential of a neuron at rest—that is, a neuron not currently receiving or sending messages—is negative, typically around -70 millivolts (mV). This is called the resting membrane potential. The negative value indicates that the inside of the membrane is relatively more negative than the outside—it is polarized. The resting potential results from two major factors: selective permeability of the membrane, and differences in ion concentration inside the cell compared to outside. Cell membranes are selectively permeable because most ions and molecules cannot cross the lipid bilayer without help, often from ion channel proteins that span the membrane. This is because the charged ions cannot diffuse through the uncharged hydrophobic interior of membranes. The most common intra- and extracellular ions found in the nervous tissue are potassium (K+), sodium (Na+…

 Core: Nervous System

Intracellular Hormone Receptors

JoVE 10876

Lipid-soluble hormones diffuse across the plasma and nuclear membrane of target cells to bind to their specific intracellular receptors. These receptors act as transcription factors that regulate gene expression and protein synthesis in the target cell

Based on their mode of action, intracellular hormone receptors are classified as Type I or Type II receptors. Type I receptors, including steroid hormone receptors such as the androgen receptor, are present in the cytoplasm. Hormone binding transports the hormone-receptor complex to the nucleus, where it binds to regulatory DNA sequences called hormone response elements and activates gene transcription. Type II receptors, such as the thyroid hormone receptor, are bound to their DNA response elements within the nucleus even in the absence of hormone. In this state, the receptor acts as an active repressor of transcription. However, upon hormone binding, the receptor-hormone complex activates transcription of thyroid hormone-inducible genes.

 Core: Endocrine System

Real-Time, Semi-Automated Fluorescent Measurement of the Airway Surface Liquid pH of Primary Human Airway Epithelial Cells

1Epithelial Research Group, Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, 2Respiratory Group, Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University, 3Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, 4Boehringer Ingelheim Pharma GmbH & Co

JoVE 59815


Estimation of Nephron Number in Whole Kidney using the Acid Maceration Method

1Department of Pharmacology and Toxicology, The University of Mississippi Medical Center, 2Department of Medicine, Division of Nephrology, Rush University Medical Center, 3Department of Medicine, Division of Nephrology, The University of Mississippi Medical Center, 4Department of Neurology, The University of Mississippi Medical Center

JoVE 58599


Transdermal Measurement of Glomerular Filtration Rate in Mice

1Division of Nephrology, Department of Medicine, Vanderbilt University Medical Center, 2Department of Cellular and Molecular Physiology, University of Liverpool, 3MediBeacon GmbH, 4Department of Veterinary Pathology and Public Health, Institute of Veterinary Science, University of Liverpool

JoVE 58520


Adaptation of Microelectrode Array Technology for the Study of Anesthesia-induced Neurotoxicity in the Intact Piglet Brain

1Department of Anesthesiology, Ohio State University College of Medicine, 2Medical Student Research Program, Ohio State University College of Medicine, 3Department of Anesthesiology and Pain Medicine, Nationwide Children's Hospital, 4Department of Neuroscience, University of Kentucky Medical Center

JoVE 57391


Transcriptomic Analysis of Human Retinal Surgical Specimens Using jouRNAl

1U968, Institut National de la Santé et de la Recherche Médicale, 2UMR S 968, Université Pierre et Marie Curie, 3UMR 7210, Centre National de la Recherche Scientifique, 4Départment d'Ophtalmologie, Centre Hospitalier Universitaire de Bordeaux

JoVE 50375


Generation of Parabiotic Zebrafish Embryos by Surgical Fusion of Developing Blastulae

1Division of Hematology/Oncology, Boston Children’s Hospital, 2Harvard Medical School, 3Division of Hematology, Department of Medicine, Brigham and Women’s Hospital, 4Harvard Stem Cell Institute, 5Broad Institute of Massachusetts Institute of Technology, 6Howard Hughes Medical Institute, 7Division of Hematologic Malignancies, Dana-Farber Cancer Institute

JoVE 54168

 Developmental Biology

Fabrication of Ti3C2 MXene Microelectrode Arrays for In Vivo Neural Recording

1Department of Bioengineering, University of Pennsylvania, 2Center for Neuroengineering and Therapeutics, University of Pennsylvania, 3Corporal Michael J. Crescenz Veterans Affairs Medical Center, 4Department of Materials Science and Engineering, Drexel University, 5A.J. Drexel Nanomaterials Institute, Drexel University, 6Department of Neurosurgery, University of Pennsylvania, 7Department of Neurology, University of Pennsylvania, 8Department of Physical Medicine and Rehabilitation

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JoVE 60741

 JoVE In-Press
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