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Gene Expression: The phenotypic manifestation of a gene or genes by the processes of Genetic transcription and Genetic translation.

Development of the Chick

JoVE 5155

The chicken embryo (Gallus gallus domesticus) provides an economical and accessible model for developmental biology research. Chicks develop rapidly and are amenable to genetic and physiological manipulations, allowing researchers to investigate developmental pathways down to the cell and molecular levels.

This video review of chick development begins by describing the…

 Biology II

Photoreceptors and Plant Responses to Light

JoVE 11115

Light plays a significant role in regulating the growth and development of plants. In addition to providing energy for photosynthesis, light provides other important cues to regulate a range of developmental and physiological responses in plants.

What Is a Photoreceptor?

Plants respond to light using a unique set of light-sensitive proteins called photoreceptors. Photoreceptors contain photopigments, which consist of a protein component bound to a non-protein, light-absorbing pigment called the chromophore. There are several different types of photoreceptors, which vary in their amino acid sequences and the type of chromophore present. These types maximally respond to different specific wavelengths of light, ranging from ultraviolet B (280-315 nanometers) to far-red (700-750 nanometers). The chromophore's absorption of light elicits structural changes in the photoreceptor, triggering a series of signal transduction events that result in gene expression changes. The Phytochrome System Many types of photoreceptors are present in plants. Phytochromes are a class of photoreceptors that sense red and far-red light. The phytochrome system acts as a natural light switch, allowing plants to respond to the intensity, duration, and color of environmental light. The phytochrome system plays a s

 Core: Biology

Intracellular Signaling Cascades

JoVE 10721

Intracellular signaling cascades amplify a signal originating extracellularly and directs it to its intended intracellular target resulting in transcription, translation, protein modifications, enzyme activation, cellular metabolism, mitosis, and/or apoptosis.

The most basic of signaling cascades involves the activation of second messengers and the release of kinases. Kinases activate or deactivate proteins and enzymes by adding a phosphate group to them. Phosphatases remove phosphate groups resulting in the deactivation or reactivation of proteins. The cyclic AMP (cAMP) pathway is named for its second messenger, cAMP. This pathway is most often initiated when a ligand binds to a G-coupled protein receptor. The G-protein decouples from the receptor and triggers adenylate cyclase to synthesize cAMP from ATP. For each ligand-receptor interaction, multiple cAMP molecules are generated—amplifying the signal. cAMP activates protein kinase A (PKA). PKA is a tetramer molecule with two regulatory subunits and two active subunits. When four cAMP molecules interact with a PKA molecule, it releases the two active subunits. These PKA subunits phosphorylate target proteins and enzymes. In the case of gene expression, PKA activates CREB, a transcription factor in the nucleus. The steps that precede the intracellular signaling cascade that is the lig

 Core: Biology

Yeast Transformation and Cloning

JoVE 5083

S. cerevisiae are unicellular eukaryotes that are a commonly-used model organism in biological research. In the course of their work, yeast researchers rely upon the fundamental technique of transformation (the uptake of foreign DNA by the cell) to control gene expression, induce genetic deletions, express recombinant proteins, and label subcellular structures.


 Biology I

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

Calcium Imaging in Neurons

JoVE 5203

Calcium ions play an integral role in neuron function: They act as intracellular signals that can elicit responses such as altered gene expression and neurotransmitter release from synaptic vesicles. Within the cell, calcium concentration is highly dynamic due to the presence of pumps that selectively transport these ions in response to a variety of signals. Calcium…


Gap Junctions

JoVE 10986

Multicellular organisms employ a variety of ways for cells to communicate with each other. Gap junctions are specialized proteins that form pores between neighboring cells in animals, connecting the cytoplasm between the two, and allowing for the exchange of molecules and ions. They are found in a wide range of invertebrate and vertebrate species, mediate numerous functions including cell differentiation and development, and are associated with numerous human diseases, including cardiac and skin disorders. Vertebrate gap junctions are composed of transmembrane proteins called connexins (CX), and six connexins form a hemichannel called a connexon. Humans have at least 21 different forms of connexins that are expressed in almost all cell types. A connexon hemichannel is said to be homomeric when all six connexins are the same, and heteromeric when composed of different types. Most cells express more than one type of connexin. These can form functional connexon hemichannels or a full gap junction channel by pairing up with a counterpart on an adjacent cell. The gap junctions are considered homotypic when each connexon is the same, and heterotypic when they differ. Clusters called gap junction plaques often form where the channels are continually recycled and degraded at the center of the plaques and replaced at the periphery. Gap junctions allow th

 Core: Biology

The Extracellular Matrix

JoVE 10695

In order to maintain tissue organization, many animal cells are surrounded by structural molecules that make up the extracellular matrix (ECM). Together, the molecules in the ECM maintain the structural integrity of tissue as well as the remarkable specific properties of certain tissues.

The extracellular matrix (ECM) is commonly composed of ground substance, a gel-like fluid, fibrous components, and many structurally and functionally diverse molecules. These molecules include polysaccharides called glycosaminoglycans (GAGs). GAGs occupy most of the extracellular space and often take up a large volume relative to their mass. This results in a matrix that can withstand tremendous forces of compression. Most GAGs are linked to proteins—creating proteoglycans. These molecules retain sodium ions based on their positive charge and therefore attract water, which keeps the ECM hydrated. The ECM also contains rigid fibers such as collagens—the primary protein component of the ECM. Collagens are the most abundant proteins in animals, making up 25% of protein by mass. A large diversity of collagens with structural similarities provide tensile strength to many tissues. Notably, tissue like skin, blood vessels, and lungs need to be both strong and stretchy to perform their physiological role. A protein called elastin gives p

 Core: Biology

Two-Dimensional Gel Electrophoresis

JoVE 5686

Two-dimensional gel electrophoresis (2DGE) is a technique that can resolve thousands of biomolecules from a mixture. This technique involves two distinct separation methods that have been coupled together: isoelectric focusing (IEF) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). This physically separates compounds across two axes of a gel by their isoelectric points…


Introduction to the Microplate Reader

JoVE 5024

The microplate reader is a multimodal instrument that allows for a variety of experiments to be performed and measured simultaneously. Microplate readers can make absorbance, fluorescence and luminescence measurements. Multiwell plates are integral to the microplate reader and allow for many experiments to be performed at once. Regardless of the assay type, experiments…

 General Laboratory Techniques

Transplantation Studies

JoVE 5336

Many developmental biologists are interested in the molecular signals and cellular interactions that induce a group of cells to develop into a particular tissue. To investigate this, scientists can use a classic technique known as transplantation, which involves tissue from a donor embryo being excised and grafted into a host embryo. By observing how transplanted tissues develop in host…

 Developmental Biology

Biological Clocks and Seasonal Responses

JoVE 11116

The circadian—or biological—clock is an intrinsic, timekeeping, molecular mechanism that allows plants to coordinate physiological activities over 24-hour cycles called circadian rhythms. Photoperiodism is a collective term for the biological responses of plants to variations in the relative lengths of dark and light periods. The period of light-exposure is called the photoperiod. One example of photoperiodism in plants is seasonal flowering. Scientists believe that plants are cued to flower by the correspondence of their circadian clocks to changes in the photoperiod. They detect these changes using light-sensitive photoreceptor systems. Phytochromes are a group of photoreceptors involved in flowering and other light-mediated processes. The phytochrome system enables plants to compare the duration of dark periods over several days. Short-day (long-night) plants flower after a minimum number of consecutive long nights. Long-day (short-night) plants, by contrast, initiate flowering following a minimum number of consecutive short nights. Phytochromes exist as two interconvertible forms: Pr and Pfr. Pr is converted into Pfr during the day, so Pfr is more abundant in daylight hours. Pfr is converted into Pr at night, so there is more Pr at nighttime. Therefore, plants can determine the length of the day-night cycle by me

 Core: Biology

Histological Staining of Neural Tissue

JoVE 5206

In order to examine the cellular, structural and molecular layout of tissues and organs, researchers use a method known as histological staining. In this technique, a tissue of interest is preserved using chemical fixatives and sectioned, or cut into very thin slices. A variety of staining techniques are then applied to provide contrast to the visually uniform sections. In …


PCR: The Polymerase Chain Reaction

JoVE 5056

The polymerase chain reaction, or PCR, is a technique used to amplify DNA through thermocycling – cyles of temperature changes at fixed time intervals. Using a thermostable DNA polymerase, PCR can create numerous copies of DNA from DNA building blocks called dinucleoside triphosphates or dNTPs. There are three steps in PCR: denaturation, annealing, and elongation. Denaturation is the …

 Basic Methods in Cellular and Molecular Biology

Seedless Vascular Plants

JoVE 11088

Seedless Vascular Plants Were the First Tall Plants on Earth

Today, seedless vascular plants are represented by monilophytes and lycophytes. Ferns—the most common seedless vascular plants—are monilophytes. Whisk ferns (and their relatives) and horsetails are also monilophytes. Lycophytes include club mosses, spikemosses, and quillworts—none of which are true mosses. Unlike nonvascular plants, vascular plants—including seedless vascular plants—have an extensive network of vascular tissue comprised of xylem and phloem. Most seedless vascular plants also have true roots and leaves. Furthermore, the life cycles of seedless vascular plants are dominated by diploid spore-producing sporophytes, rather than gametophytes. However, like nonvascular plants, seedless vascular plants reproduce with spores rather than seeds. Seedless vascular plants are also typically more reproductively successful in moist environments because their sperm require a film of water to reach the eggs. The Life Cycle of Seedless Vascular Plants Like animals, seedless vascular plants (and other plants) alternate between meiosis and fertilization during reproduction. Meiosis is a cell division process that produces haploid cells—which contain one complete set of chromosomes—from a diploid cell&

 Core: Biology

Internal Receptors

JoVE 11011

Many cellular signals are hydrophilic and therefore cannot pass through the plasma membrane. However, small or hydrophobic signaling molecules can cross the hydrophobic core of the plasma membrane and bind to internal, or intracellular, receptors that reside within the cell. Many mammalian steroid hormones use this mechanism of cell signaling, as does nitric oxide (NO) gas.

Similar to membrane-bound receptors, binding of a ligand to a receptor located in the cytoplasm or nucleus of a cell causes a conformational change in the receptor. Like transcription factors, the active receptor can bind to receptor-specific DNA binding sites to increase or decrease the transcription of target genes. In the case of an intracellular receptor located in the cytoplasm, the receptor-ligand complex must first cross the nuclear membrane. Many steroid hormones, including estrogen and testosterone, use intracellular receptors to induce specific effects. As an example, estrogen can diffuse across the membrane; binding of estrogen to its receptor results in dimerization of the receptors and transport of the ligand-receptor complex to the nucleus. Once in the nucleus, the complex can bind to DNA sequences called Estrogen-Response Elements (EREs). Depending on the other transcription factors and co-activators, binding of activated estrogen receptors (ERs) to EREs may cause an incre

 Core: Biology

What is Cell Signaling?

JoVE 10985

Despite the protective membrane that separates a cell from the environment, cells need the ability to detect and respond to environmental changes. Additionally, cells often need to communicate with one another. Unicellular and multicellular organisms use a variety of cell signaling mechanisms to communicate to respond to the environment.

Cells respond to many types of information, often through receptor proteins positioned on the membrane. For example, skin cells respond to and transmit touch information, while photoreceptors in the retina can detect light. Most cells, however, have evolved to respond to chemical signals, including hormones, neurotransmitters, and many other types of signaling molecules. Cells can even coordinate different responses elicited by the same signaling molecule. Typically, cell signaling involves three steps: (1) reception of the signal, (2) signal transduction, and (3) a response. In most signal reception, a membrane-impermeable molecule, or ligand, causes a change in a membrane receptor; however, some signaling molecules, such as hormones, can traverse the membrane to reach their internal receptors. The membrane receptor can then send this signal to intracellular messengers, which transduces the message into a cellular response. This intracellular response may include a change transcription, translation, protein activation,

 Core: Biology

Chick ex ovo Culture

JoVE 5157

One strength of the chicken (Gallus gallus domesticus) as a model organism for developmental biology is that the embryo develops outside the female and is easily accessible for experimental manipulation. Many techniques allow scientists to examine chicken embryos inside the eggshell (in ovo), but embryonic access can be limited at later stages of development.…

 Biology II

Comprehensive Workflow for the Genome-wide Identification and Expression Meta-analysis of the ATL E3 Ubiquitin Ligase Gene Family in Grapevine

1Dipartimento di Biotecnologie, Università degli Studi di Verona, 2Ecology and Evolution, Research School of Biology, The Australian National University, 3Dipartimento di Agraria, SACEG, Università degli Studi di Sassari

JoVE 56626


Quantification of Information Encoded by Gene Expression Levels During Lifespan Modulation Under Broad-range Dietary Restriction in C. elegans

1Centre for Developmental Neurobiology, King's College London, 2Interdisciplinary Bioengineering Graduate Program, Georgia Institute of Technology, 3Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 4School of Chemical & Biomolecular Engineering, Georgia Institute of Technology

JoVE 56292


Gene Expression Analysis of Endothelial Cells Exposed to Shear Stress Using Multiple Parallel-plate Flow Chambers

1Institute of Medical Science, University of Toronto, 2Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, 3Department of Laboratory Medicine and Pathobiology, University of Toronto, 4Department of Medicine, University of Toronto

JoVE 58478


Laser Capture Microdissection of Highly Pure Trabecular Meshwork from Mouse Eyes for Gene Expression Analysis

1Immunity, Inflammation, and Disease Laboratory, Division of Intramural Research, National Institute of Environmental Health Sciences, NIH, 2Cellular and Molecular Pathology Branch, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, NIH, 3Integrated Laboratory Systems Inc., 4Experimental Pathology Laboratories Inc.

JoVE 57576


A Multilayer Microfluidic Platform for the Conduction of Prolonged Cell-Free Gene Expression

1Institute for Complex Molecular Systems, Department of Biomedical Engineering, Computational Biology Group, Eindhoven University of Technology, 2Institute for Molecules and Materials, Radboud University, 3Institute of Bioengineering, School of Engineering École Polytechnique Fédérale de Lausanne (EPFL)

JoVE 59655

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