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Muscle Cells: Mature contractile cells, commonly known as myocytes, that form one of three kinds of muscle. The three types of muscle cells are skeletal (Muscle fibers, Skeletal), cardiac (Myocytes, Cardiac), and smooth (Myocytes, Smooth muscle). They are derived from embryonic (precursor) muscle cells called Myoblasts.

Skeletal Muscle Anatomy

JoVE 10867

Skeletal muscle is the most abundant type of muscle in the body. Tendons are the connective tissue that attaches skeletal muscle to bones. Skeletal muscles pull on tendons, which in turn pull on bones to carry out voluntary movements.

Skeletal muscles are surrounded by a layer of connective tissue called epimysium, which helps protect the muscle. Beneath the epimysium, an additional layer of connective tissue, called perimysium, surrounds and groups together subunits of skeletal muscle called fasciculi. Each fascicle is a bundle of skeletal muscle cells, or myocytes, which are often called skeletal muscle fibers due to their size and cylindrical appearance. Between the muscle fibers is an additional layer of connective tissue called endomysium. The muscle fiber membrane is called the sarcolemma. Each muscle fiber is made up of multiple rod-like chains called myofibrils, which extend across the length of the muscle fiber and contract. Myofibrils contain subunits called sarcomeres, which are made up of actin and myosin in thin and thick filaments, respectively. Actin contains myosin-binding sites that allow thin and thick filaments to connect, forming cross bridges. For a muscle to contract, accessory proteins that cover myosin-binding sites on thin filaments must be displaced to enable the formation of cross bridges. During muscle contracti

 Core: Biology

Cell Structure- Concept

JoVE 10587


Cells represent the most basic biological units of all organisms, whether it be simple, single-celled organisms like bacteria, or large, multicellular organisms like elephants and giant redwood trees. In the mid 19th century, the Cell Theory was proposed to define a cell, which states:

Every living organism is made up of one or more cells.
The cells…

 Lab Bio

Cell Division- Concept

JoVE 10571

Cell division is fundamental to all living organisms and required for growth and development. As an essential means of reproduction for all living things, cell division allows organisms to transfer their genetic material to their offspring. For a unicellular organism, cellular division generates a completely new organism. For multicellular organisms, cellular division produces new cells for…

 Lab Bio


JoVE 10696

Cells with similar structure and function are grouped into tissues. A group of tissues with a specialized function is called an organ. There are four main types of tissue in vertebrates: epithelial, connective, muscle, and nervous.

Epithelial tissue consists of thin sheets of cells and includes the skin and the linings of internal organs and body cavities. Epithelial cells are tightly packed, providing a barrier against injury, infection, and water loss. Epithelial tissue can be a single layer called simple epithelium, or multiple layers called stratified epithelium. In stratified epithelium, such as the skin, the outer cells—which are subject to damage—are replaced through the division of cells underneath. Epithelial cells have a variety of shapes, including squamous (flattened), cuboid, and columnar. Some epithelial tissues absorb or secrete substances, such as the lining of the intestines. Connective tissue is composed of cells within an extracellular matrix and includes loose connective tissue, fibrous connective tissue, adipose (fat) tissue, cartilage, bone, and blood. Although the characteristics of connective tissue vary greatly, their general function is to support and attach multiple tissues. For example, tendons are made of fibrous connective tissue and attach muscle to bone. Blood transports oxygen, nutrients and waste produ

 Core: Biology

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: Biology

Paracrine Signaling

JoVE 10716

Paracrine signaling allows cells to communicate with their immediate neighbors via secretion of signaling molecules. The signal only triggers a response in nearby target cells as the signal molecules degrade quickly or are inactivated by nearby cells if not taken up. Prominent examples of paracrine signaling include nitric oxide signaling in blood vessels, synaptic signaling of neurons, the blood clotting system, tissue repair/wound healing, and local allergic skin reactions. One of the essential paracrine signaling molecules is the gas nitric oxide (NO). Nitric oxide is produced by a family of enzymes known as nitric oxide synthases. Blood vessels contain several layers of cells. The innermost layer of cells is the endothelium. Endothelial cells have nitric oxide synthase, which produces nitric oxide that diffuses in all directions. The nitric oxide that reaches the blood does not contribute to signaling but immediately reacts with biochemicals, such as hemoglobin. Nitric oxide molecules that diffuse in the opposite direction, towards the next layer of the blood vessel, participate in some important signaling. The layer just exterior to the endothelium is made up of smooth muscle cells. The function of smooth muscle cells is to contract. When these cells contract, they clamp down on the blood vessel, narrowing its diameter and consequently rais

 Core: Biology

Tissue Regeneration with Somatic Stem Cells

JoVE 5339

Somatic or adult stem cells, like embryonic stem cells, are capable of self-renewal but demonstrate a restricted differentiation potential. Nonetheless, these cells are crucial to homeostatic processes and play an important role in tissue repair. By studying and manipulating this cell population, scientist may be able to develop new regenerative therapies for injuries and diseases.

 Developmental Biology

Motor Units

JoVE 10871

A motor unit consists of two main components: a single efferent motor neuron (i.e., a neuron that carries impulses away from the central nervous system) and all of the muscle fibers it innervates. The motor neuron may innervate multiple muscle fibers, which are single cells, but only one motor neuron innervates a single muscle fiber.

Lower motor neurons are efferent neurons that control skeletal muscle, the most abundant type of muscle in the body. The cell bodies of lower motor neurons are located in the spinal cord or brain stem. Those in the brainstem transmit nerve signals through the cranial nerve, and primarily control muscles in the head and neck. Lower motor neurons originating in the spinal cord send signals along the spinal nerve, and primarily control muscles in the limbs and body trunk. A lower motor neuron fires an action potential that, at once, contract all skeletal muscle cells that the neuron innervates. Thus, motor units are functional units of skeletal muscle. The size of a motor unit, or the number of muscle fibers the lower motor neuron innervates, varies depending on the size of the muscle and the speed and precision the movement requires. Muscles in the eyes and fingers, which require rapid, precise control, are generally controlled by small motor units. In these units, motor neurons connect to a small number of muscle f

 Core: Biology


JoVE 10794

Transcription is the process of synthesizing RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene sequence. Additionally, many other proteins and regulatory sequences are involved in the proper synthesis of messenger RNA (mRNA). Regulation of transcription is responsible for the differentiation of all the different types of cells and often for the proper cellular response to environmental signals. In eukaryotes, the DNA is first transcribed into a primary RNA, or pre-mRNA, that can be further processed into a mature mRNA to serve as a template for the synthesis of proteins. In prokaryotes such as bacteria, however, translation of RNA into polypeptides can begin while the transcription is still ongoing, as RNA can be quickly degraded. Transcription can also produce different kinds RNA molecules that do not code for protein, such as microRNAs, transfer RNA (tRNA), and ribosomal RNA (rRNA)—all of which contribute to protein synthesis. With few exceptions, all of the cells in the human body have the same genetic information in them, from neurons in the brain to muscle cells in the heart. So how do cells assume such diverse forms and functions? To a large extent, the answer lies in the regulation of transcription during development of the organism. Specifically, transcriptional regulation plays a central ro

 Core: Biology

Embryonic Stem Cell Culture and Differentiation

JoVE 5332

Culturing embryonic stem (ES) cells requires conditions that maintain these cells in an undifferentiated state to preserve their capacity for self-renewal and pluripotency. Stem cell biologists are continuously optimizing methods to improve the efficiency of ES cell culture, and are simultaneously trying to direct the differentiation of ES cells into specific cell types that could be used in…

 Developmental Biology

Ion Channels

JoVE 10722

Ion channels maintain the membrane potential of a cell. For most cells, especially excitable ones, the inside has a more negative charge than the outside of the cell, due to a greater number of negative ions than positive ions. For excitable cells, like firing neurons, contracting muscle cells, or sensory touch cells, the membrane potential must be able to change rapidly moving from a negative membrane potential to one that is more positive. To achieve this, cells rely on two types of ion channels: ligand-gated and voltage-gated. Ligand-gated ion channels, also called ionotropic receptors, are transmembrane proteins that form a channel but which also have a binding site. When a ligand binds to the surface, it opens the ion channel. Common ionotropic receptors include the NMDA, kainate, and AMPA glutamate receptors and the nicotinic acetylcholine receptors. While the majority of ionotropic receptors are activated by extracellular binding of neurotransmitters such as glutamate or acetylcholine, a few can be intracellularly activated by ions themselves. When a ligand, like glutamate or acetylcholine, binds to its receptor it allows the influx of sodium (Na+) and calcium (Ca2+) ions into the cells. The positive ions, or cations, follow down their electrochemical gradient, moving from the more positive extracellular surface to the less p

 Core: Biology

Induced Pluripotency

JoVE 5333

Induced pluripotent stem cells (iPSCs) are somatic cells that have been genetically reprogrammed to form undifferentiated stem cells. Like embryonic stem cells, iPSCs can be grown in culture conditions that promote differentiation into different cell types. Thus, iPSCs may provide a potentially unlimited source of any human cell type, which is a major breakthrough in the field of regenerative…

 Developmental Biology


JoVE 10694

Mitochondria and peroxisomes are organelles that are the primary sites of oxygen usage in eukaryotic cells. Mitochondria carry out cellular respiration—the process that converts energy from food into ATP—the primary form of energy used by cells. Peroxisomes carry out a variety of functions, primarily breaking down different substances such as fatty acids.

Peroxisomes contain up to 50 enzymes and are surrounded by a single membrane. They carry out oxidative reactions that break down molecules and produce hydrogen peroxide (H2O2) as a by-product. H2O2 is toxic to cells, but the peroxisome contains an enzyme—catalase—that converts H2O2 into harmless water and oxygen. In addition, catalase uses H2O2 to break down alcohol in the liver into aldehyde and water. However, since H2O2 is produced in very low quantities in the body, other enzymes primarily degrade alcohol. A critical function of the peroxisome is to break down fatty acids in a process called β oxidation. The resulting product—acetyl-CoA—is released into the cytosol and can travel to the mitochondria, where it is used to produce ATP. In mammalian cells, the mitochondria also carry out β oxidation, as well as using products from the catabolism o

 Core: Biology

Cellular Respiration- Concept

JoVE 10567

Autotrophs and Heterotrophs

Living organisms require a continuous input of energy to maintain cellular and organismal functions such as growth, repair, movement, defense, and reproduction. Cells can only use chemical energy to fuel their functions, therefore they need to harvest energy from chemical bonds of biomolecules, such as sugars and lipids. Autotrophic organisms, namely…

 Lab Bio


JoVE 10967

The cytoplasm consists of organelles, an aqueous solution called the cytosol, and a framework of protein scaffolds called the cytoskeleton. The cytosol is a rich broth of ions, small organic molecules such as glucose, and macromolecules such as proteins. Several cellular processes including protein synthesis occur in the cytoplasm.

The composition of the cytosol promotes protein folding such that hydrophobic amino acid side chains are oriented away from the aqueous solution and towards the protein core. However, cellular stressors such as aging and changes in pH, temperature, or osmolarity cause protein misfolding. Misfolded proteins may aggregate to form insoluble deposits in the cytoplasm. Insoluble protein aggregates are implicated in neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis. The eukaryotic cytoskeleton consists of three types of filamentous proteins: microtubules, microfilaments, and intermediate filaments. Microtubules–the largest type of filament–are made up of the protein tubulin. Microtubules are dynamic structures that can grow or shrink by adding or removing tubulin molecules from the ends of their strands. They provide structural stability and provide tracks for the transport of proteins and vesicles within the cell. In addition, microtu

 Core: Biology

Facilitated Transport

JoVE 10705

The chemical and physical properties of plasma membranes cause them to be selectively permeable. Since plasma membranes have both hydrophobic and hydrophilic regions, substances need to be able to transverse both regions. The hydrophobic area of membranes repel substances such as charged ions. Therefore, such substances need special membrane proteins to cross a membrane successfully. In the process of facilitated transport, also known as facilitated diffusion, molecules and ions travel across a membrane via two types of membrane transport proteins: channels and carrier proteins. These membrane transport proteins enable diffusion without requiring additional energy. Channel proteins form a hydrophilic pore through which charged molecules can pass through, thus avoiding the hydrophobic layer of the membrane. Channel proteins are specific for a given substance. For example, aquaporins are channel proteins that specifically facilitate the transport of water through the plasma membrane. Channel proteins are either always open or gated by some mechanism to control flow. Gated channels remain closed until a particular ion or substance binds to the channel, or some other mechanism occurs. Gated channels are found in the membranes of cells such as muscle cells and nerve cells. Muscle contractions occur when the relative concentrations of ions on the interior and

 Core: Biology

The Nucleus

JoVE 10691

The nucleus is a membrane-bound organelle that contains a eukaryotic organism’s genetic instructions in the form of chromosomal DNA. This is distinct from the DNA in mitochondria or chloroplasts that carry out functions specific to those organelles. While some cells—such as red blood cells—do not have a nucleus, and others—such as skeletal muscle cells—have multiple nuclei, most eukaryotic cells have a single nucleus. The DNA in the nucleus is wrapped around proteins such as histones, creating a DNA-protein complex called chromatin. When cells are not dividing—that is, when they are in the interphase part of their cell cycle—the chromatin is organized diffusely. This allows easy access to the DNA during the transcription process when messenger RNA (mRNA) is synthesized based on the DNA code. When a eukaryotic cell is about to divide, the chromatin condenses tightly into distinct, linear chromosomes. Humans have 46 chromosomes in total. Chromatin is particularly concentrated in a region of the nucleus called the nucleolus. The nucleolus is important for the production of ribosomes, which translate mRNA into protein. In the nucleolus, ribosomal RNA is synthesized and combined with proteins to create ribosomal subunits, which later form functioning ribosomes in the cytoplasm of the cell. The interior of t

 Core: Biology

Neuron Structure

JoVE 10842

Neurons are the main type of cell in the nervous system that generate and transmit electrochemical signals. They primarily communicate with each other using neurotransmitters at specific junctions called synapses. Neurons come in many shapes that often relate to their function, but most share three main structures: an axon and dendrites that extend out from a cell body.

The neuronal cell body—the soma— houses the nucleus and organelles vital to cellular function. Extending from the cell body are thin structures that are specialized for receiving and sending signals. Dendrites typically receive signals while the axon passes on the signals to other cells, such as other neurons or muscle cells. The point at which a neuron makes a connection to another cell is called a synapse. Neurons receive inputs primarily at postsynaptic terminals, which are frequently located on spines—small bumps protruding from the dendrites. These specialized structures contain receptors for neurotransmitters and other chemical signals. Dendrites are often highly branched, allowing some neurons to receive tens of thousands of inputs. Neurons most commonly receive signals at their dendrites, but they can also have synapses in other areas, such as the cell body. The signal received at the synapses travels down the dendrite to the soma, where the cell can proce

 Core: Biology

An Introduction to Cell Motility and Migration

JoVE 5643

Cell motility and migration play important roles in both normal biology and in disease. On one hand, migration allows cells to generate complex tissues and organs during development, but on the other hand, the same mechanisms are used by tumor cells to move and spread in a process known as cancer metastasis. One of the primary cellular machineries that make cell movement…

 Cell Biology

What is Cellular Respiration?

JoVE 10976

Organisms harvest energy from food, but this energy cannot be directly used by cells. Cells convert the energy stored in nutrients into a more usable form: adenosine triphosphate (ATP).

ATP stores energy in chemical bonds that can be quickly released when needed. Cells produce energy in the form of ATP through the process of cellular respiration. Although much of the energy from cellular respiration is released as heat, some of it is used to make ATP. During cellular respiration, several oxidation-reduction (redox) reactions transfer electrons from organic molecules to other molecules. Here, oxidation refers to electron loss and reduction to electron gain. The electron carriers NAD+ and FAD—and their reduced forms, NADH and FADH2, respectively—are essential for several steps of cellular respiration. Some prokaryotes use anaerobic respiration, which does not require oxygen. Most organisms use aerobic (oxygen-requiring) respiration, which produces much more ATP. Aerobic respiration generates ATP by breaking down glucose and oxygen into carbon dioxide and water. Both aerobic and anaerobic respiration begin with glycolysis, which does not require oxygen. Glycolysis breaks down glucose into pyruvate, yielding ATP. In the absence of oxygen, pyruvate ferments, producing NAD+ for continued glyc

 Core: Biology

What is Gene Expression?

JoVE 10797

Gene expression is the process in which DNA directs the synthesis of functional products, such as proteins. Cells can regulate gene expression at various stages. It allows organisms to generate different cell types and enables cells to adapt to internal and external factors.

A gene is a stretch of DNA that serves as the blueprint for functional RNAs and proteins. Since DNA is made up of nucleotides and proteins consist of amino acids, a mediator is required to convert the information that is encoded in DNA into proteins. This mediator is the messenger RNA (mRNA). mRNA copies the blueprint from DNA by a process called transcription. In eukaryotes, transcription takes place in the nucleus by complementary base-pairing with the DNA template. The mRNA is then processed and transported into the cytoplasm where it serves as a template for protein synthesis during translation. In prokaryotes, which lack a nucleus, the processes of transcription and translation occur at the same location and almost simultaneously since the newly-formed mRNA is susceptible to rapid degradation. Every cell of an organism contains the same DNA, and consequently the same set of genes. However, not all genes in a cell are “turned on” or use to synthesize proteins. A gene is said to be “expressed” when the protein it encodes is produced by the cell. Gen

 Core: Biology

Endoplasmic Reticulum

JoVE 10969

The Endoplasmic Reticulum (ER) in eukaryotic cells is a substantial network of interconnected membranes with diverse functions, from calcium storage to biomolecule synthesis. A primary component of the endomembrane system, the ER manufactures phospholipids critical for membrane function throughout the cell. Additionally, the two distinct regions of the ER specialize in the manufacture of specific lipids and proteins. The rough ER is characterized by the presence of microscopically-visible ribosomes on its surface. As a ribosome begins translation of an mRNA in the cytosol, the presence of a signal sequence directs the ribosome to the surface of the rough ER. A receptor in the membrane of the ER recognizes this sequence and facilitates the entry of the growing polypeptide into the ER lumen through a transmembrane protein complex. With the assistance of chaperones, nascent proteins fold and undergo other functional modifications, including glycosylation, disulfide bond formation, and oligomerization. Properly folded and modified proteins are then packaged into vesicles to be shipped to the Golgi apparatus and other locations in the cell. Chaperones identify improperly folded proteins and facilitate degradation in the cytosol by proteasomes. Lacking ribosomes, the smooth ER is the cellular location of lipid and steroid synthesis, cellular detoxification,

 Core: Biology

Complementary DNA

JoVE 10818

Only genes that are transcribed into messenger RNA (mRNA) are active, or expressed. Scientists can, therefore, extract the mRNA from cells to study gene expression in different cells and tissues. The scientist converts mRNA into complementary DNA (cDNA) via reverse transcription. Because mRNA does not contain introns (non-coding regions) and other regulatory sequences, cDNA—unlike genomic DNA—also allows researchers to directly determine the amino acid sequence of the peptide encoded by the gene. cDNA can be generated by several methods, but a common way is to first extract total RNA from cells, and then isolate the mRNA from the more predominant types—transfer RNA (tRNA) and ribosomal (rRNA). Mature eukaryotic mRNA has a poly(A) tail—a string of adenine nucleotides—added to its 3’ end, while other types of RNA do not. Therefore, a string of thymine nucleotides (oligo-dTs) can be attached to a substrate such as a column or magnetic beads, to specifically base-pair with the poly(A) tails of mRNA. While mRNA with a poly(A) tail is captured, the other types of RNA are washed away. Next, reverse transcriptase—a DNA polymerase enzyme from retroviruses—is used to generate cDNA from the mRNA. Since, like most DNA polymerases, reverse transcriptase can add nucleotides only to the 3’ end of a chain, a pol

 Core: Biology

Using TMS to Measure Motor Excitability During Action Observation

JoVE 10270

Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel—University of Southern California

Transcranial Magnetic Stimulation (TMS) is a non-invasive brain stimulation technique that involves passing current through an insulated coil placed against the scalp. A brief magnetic field is created by current in the coil, and because of…


Overview of Tissue Engineering

JoVE 5785

Tissue engineering is an emerging field, which aims to create artificial tissue from biomaterials, specific cells and growth factors. These engineered tissue constructs have far-reaching benefits, with possibilities for organ replacement and tissue repair.

This video introduces the field of tissue engineering and examines the components …


The ATP Bioluminescence Assay

JoVE 5653

In fireflies, the luciferase enzyme converts a compound called luciferin into oxyluciferin, and produces light or “luminescence” as a result. This reaction requires energy derived from ATP in order to proceed, so researchers have exploited the luciferase-luciferin interaction to gauge ATP levels in cells. Given ATP’s role as the cell’s currency of…

 Cell Biology

G-protein Coupled Receptors

JoVE 10718

G-protein coupled receptors are ligand binding receptors that indirectly affect changes in the cell. The actual receptor is a single polypeptide that transverses the cell membrane seven times creating intracellular and extracellular loops. The extracellular loops create a ligand specific pocket which binds to neurotransmitters or hormones. The intracellular loops holds onto the G-protein.

The G-protein or guanine nucleotide-binding protein, is a large heterotrimeric complex. Its three subunits are labeled alpha (α), beta (β), and gamma (γ). When the receptor is unbound or resting, the α-subunit binds a guanosine diphosphate molecule or GDP, and all three subunits are attached to the receptor. When a ligand binds the receptor, the α-subunit releases the GDP and binds a molecule of guanosine triphosphate (GTP). This action releases the α-GTP complex and the β-γ complex from the receptor. The α-GTP can move along the membrane to activate second messenger pathways such as cAMP. However there are different types of α-subunits and some are inhibitory, turning off cAMP. The β-γ complex may interact with potassium ion channels which release potassium (K+) into the extracellular space resulting in hyperpolarization of the cell membrane. This type of ligand-gated ion channel is called a G-prot

 Core: Biology


JoVE 10745

Most eukaryotic organisms require oxygen to survive and function adequately. Such organisms produce large amounts of energy during aerobic respiration by metabolizing glucose and oxygen into carbon dioxide and water. However, most eukaryotes can generate some energy in the absence of oxygen by anaerobic metabolism.

Aerobic respiration proceeds through a series of oxidation-reduction reactions that end when oxygen–the final electron acceptor–is reduced to water. In the absence of oxygen, this reaction cannot proceed. Instead, cells regenerate NADH produced during glycolysis by using an organic molecule, such as pyruvate, as the final electron acceptor. The process of using an organic molecule to regenerate NAD+ from NADH is called fermentation. There are two types of fermentation based on the end products of the reaction: 1) lactic acid fermentation and 2) alcohol fermentation. In mammals, lactic acid fermentation takes place in red blood cells that cannot respire aerobically due to lack of mitochondria, as well as in skeletal muscles during strenuous exercise. It also occurs in certain bacteria, like those found in yogurt. In this reaction, pyruvate and NADH are converted to lactic acid and NAD+. Alcohol fermentation is a two-step process. In the first step, pyruvate is converted to carbon dioxide and acetaldehyde

 Core: Biology

Explant Culture of Neural Tissue

JoVE 5209

The intricate structure of the vertebrate nervous system arises from a complex series of events involving cell differentiation, cell migration, and changes in cell morphology. Studying these processes is essential to our understanding of nervous system function as well as our ability to diagnose and treat disorders that result from abnormal development. However, neural…


Sex-linked Disorders

JoVE 10981

Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in biological deficits, the disorder is considered sex-linked.

Y chromosome mutations are called “Y-linked” and only affect males since they alone carry a copy of that chromosome. Mutations to the relatively small Y chromosome can impact male sexual function and secondary sex characteristics. Y-chromosome infertility is a disorder that affects sperm production, caused by deletions to the azoospermia factor (AZF) regions of the Y chromosome. In general, Y-linked disorders are only passed from father to son; however, because affected males typically do not father children without assisted reproductive technologies, Y-chromosome infertility is not typically passed on to offspring. X-linked disorders can be either dominant or recessive. X-linked dominant disorders are the result of a mutation to the X chromosome that can affect either males or females. However, some disorders, including Fragile X syndrome, affect males more severely than females, likely because males do not have a second, normal copy of the X chromosome. Fragile X syndrome is characterized by a wide range of developmental problems, including learning disabilities. X-linked hypophosphatemia is another X-linked dominant condition that manifes

 Core: Biology

Evaluating the Heat Transfer of a Spin-and-Chill

JoVE 10440

Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA

The Spin-and-Chill uses heat transfer and fluid flow fundamentals to chill beverages from room temperature to 38 °F in as little as 2 min. It would take a refrigerator approximately 240 min and an ice chest…

 Chemical Engineering

Anatomy of the Heart

JoVE 10886

The human heart is made up of three layers of tissue that are surrounded by the pericardium, a membrane that protects and confines the heart. The outermost layer, closest to the pericardium, is the epicardium. The pericardial cavity separates the pericardium from the epicardium. Beneath the epicardium is the myocardium, the middle layer, and the endocardium, the innermost layer. There are four chambers of the heart: the right atrium, the right ventricle, the left atrium, and the left ventricle. These compartments have two types of valves—atrioventricular and semilunar—that prevent blood from flowing in the wrong direction. The right atrium receives blood from the coronary sinus and the superior and inferior vena cavae. This blood goes into the right ventricle via the right atrioventricular (or tricuspid) valve, a flap of connective tissue that prevents the backflow of blood into the atrium. Then, the blood leaves the heart, traveling through the pulmonary semilunar valve into the pulmonary artery. Blood is then carried back into the left atrium of the heart by the pulmonary veins. Between the left atrium and the left ventricle, the blood is again passed through an atrioventricular valve that prevents backflow into the atrium. This atrioventricular valve is called the bicuspid (or mitral) valve. The blood passes through the left ventricle into the aorta

 Core: Biology

Preparation and Utilization of Freshly Isolated Human Detrusor Smooth Muscle Cells for Characterization of 9-Phenanthrol-Sensitive Cation Currents

1Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, 2Department of Urology, Medical University of South Carolina, 3Department of Urology, College of Medicine, University of Tennessee Health Science Center, 4Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center

JoVE 59884

 Immunology and Infection

Measurement of Maximum Isometric Force Generated by Permeabilized Skeletal Muscle Fibers

1Department of Orthopaedic Surgery, University of Michigan Medical School, 2Department of Molecular & Integrative Physiology, University of Michigan Medical School, 3Department of Biomedical Engineering, University of Michigan Medical School, 4Department of Surgery, Section of Plastic Surgery, University of Michigan Medical School

JoVE 52695


Quantitative Analysis of Cellular Composition in Advanced Atherosclerotic Lesions of Smooth Muscle Cell Lineage-Tracing Mice

1Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh, 2Robert M. Berne Cardiovascular Research Center, University of Virginia, 3Department of Biochemistry and Molecular Genetics, University of Virginia, 4Division of Cardiology, University of Pittsburgh School of Medicine

JoVE 59139

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