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Cell Death: The termination of the cell's ability to carry out vital functions such as metabolism, growth, reproduction, responsiveness, and adaptability.

Contact-dependent Signaling

JoVE 10715

Contact-dependent signaling uses specialized cytoplasmic channels between cells that allow the flow of small molecules between them. In animal cells, these channels are called gap junctions. In plants, they are known as plasmodesmata.

Gap junctions form when two hemichannels, or connexons, join; one connexon from one cell coupling to a connexon of an adjacent cell. Each cell’s connexon is formed from six proteins creating a circular channel. There are over 20 different types of these proteins, or connexins, so there is substantial variation in how they come together as connexons and as gap junctions. Connexins have four transmembrane subunits with both their N- and C-terminus endings located intracellularly. The C-terminus has multiple phosphorylation sites so it can be activated by numerous different kinases- further adding to gap junction variety. Depending on the activating kinase, and the C-terminal amino acid residues of connexins that are phosphorylated, gap junctions can be partially or fully opened. This selectively allows small molecules to flow from one cell into another. A gap junction may also exclude by electrochemical charge. The selectivity of gap junctions allows a single cell to coordinate a complex multicellular response. However, some toxic molecules, matching the size and electrochemical preference of the gap junction, can also p

 Core: Biology

Annexin V and Propidium Iodide Labeling

JoVE 5650

Staining with annexin V and propidium iodide (PI) provides researchers with a way to identify different types of cell death—either necrosis or apoptosis. This technique relies on two components. The first, annexin V, is a protein that binds certain phospholipids called phosphatidylserines, which normally occur only in the inner, cytoplasm-facing leaflet of a…

 Cell Biology

Inflammation

JoVE 10902

In response to tissue injury and infection, mast cells initiate inflammation. Mast cells release chemicals that increase the permeability of adjacent blood capillaries and attract additional immune cells to the wound or site of infection. Neutrophils are phagocytic leukocytes that exit the bloodstream and engulf invading microbes. Blood clotting platelets seal the wound and fibers create a scaffold for wound healing. Macrophages engulf aging neutrophils to end the acute inflammatory response. Tissue injury and infection are the primary causes of acute inflammation. Inflammation protects the body by eliminating the cause of tissue injury and initiating the removal of cell debris resulting from the initial damage and related immune cell activity. Inflammation involves mediators of both the innate and adaptive immune system. Proper regulation of inflammation is crucial to clear the pathogen and remove cell debris without overly damaging healthy tissue in the process. If inflammatory processes are not properly regulated, chronic inflammation can arise that is often fatal. Mast cells are the first to respond to tissue injury, as they are primarily located in areas that have contact with the exterior: the skin, gut, and airways. Mast cells have an arsenal of receptors on their cell surface and can hence be activated by a wide variety of stimuli, such as mi

 Core: Biology

Adult Stem Cells

JoVE 10810

Stem cells are undifferentiated cells that divide and produce more stem cells or progenitor cells that differentiate into mature, specialized cell types. All the cells in the body are generated from stem cells in the early embryo, but small populations of stem cells are also present in many adult tissues including the bone marrow, brain, skin, and gut. These adult stem cells typically produce the various cell types found in that tissue—to replace cells that are damaged or to continuously renew the tissue. The epithelium lining the small intestine is continuously renewed by adult stem cells. It is the most rapidly replaced tissue in the human body, with most cells being replaced within 3-5 days. The intestinal epithelium consists of thousands of villi that protrude into the interior of the small intestine—increasing its surface area to aid in the absorption of nutrients. Intestinal stem cells are located at the base of invaginations called crypts that lie between the villi. They divide to produce new stem cells, as well as daughter cells (called transit amplifying cells) that divide rapidly, move up the villi and differentiate into all the cell types in the intestinal epithelium, including absorptive, goblet, enteroendocrine, and Paneth cells. These mature cells continue to move up the villi as they carry out their functions, except Paneth cell

 Core: Biology

An Introduction to Cell Metabolism

JoVE 5652

In cells, critical molecules are either built by joining together individual units like amino acids or nucleotides, or broken down into smaller components. Respectively, the reactions responsible for this are referred to as anabolic and catabolic. These reactions require or produce energy typically in the form of a “high-energy” molecule called ATP. Together,…

 Cell Biology

An Introduction to Saccharomyces cerevisiae

JoVE 5081

Saccharomyces cerevisiae (commonly known as baker’s yeast) is a single-celled eukaryote that is frequently used in scientific research. S. cerevisiae is an attractive model organism due to the fact that its genome has been sequenced, its genetics are easily manipulated, and it is very easy to maintain in the lab. Because many yeast proteins are similar in sequence and function…

 Biology I

Yeast Maintenance

JoVE 5095

Research performed in the yeast Saccharomyces cerevisiae has significantly improved our understanding of important cellular phenomona such as regulation of the cell cycle, aging, and cell death. The many benefits of working with S. cerevisiae include the facts that they are inexpensive to grow in the lab and that many ready-to-use strains are now commercially available. Nevertheless,…

 Biology I

Serial Dilutions and Plating: Microbial Enumeration

JoVE 10507

Source: Jonathan F. Blaize1, Elizabeth Suter1, and Christopher P. Corbo1
1 Department of Biological Sciences, Wagner College, 1 Campus Road, Staten Island NY, 10301


Quantitative assessment of prokaryotes can be onerous given their abundance, propensity for exponential proliferation, species diversity within a population, and specific …

 Microbiology

RNA Splicing

JoVE 10802

The process in which eukaryotic RNA is edited prior to protein translation is called splicing. It removes regions that do not code for proteins and patches the protein-coding regions together. Splicing also allows several protein variants to be expressed from a single gene and plays an essential role in development, tissue differentiation, and adaptation to environmental stress. Errors in splicing can lead to diseases such as cancer. The RNA strand transcribed from eukaryotic DNA is called the primary transcript. The primary transcripts designated to become mRNA are called precursor messenger RNA (pre-mRNA). The pre-mRNA is then processed to form mature mRNA that is suitable for protein translation. Eukaryotic pre-mRNA contains alternating sequences of exons and introns. Exons are nucleotide sequences that code for proteins whereas introns are the non-coding regions. RNA splicing is the process by which introns are removed and exons patched together. Splicing is mediated by the spliceosome—a complex of proteins and RNA called small nuclear ribonucleoproteins (snRNPs). The spliceosome recognizes specific nucleotide sequences at exon/intron boundaries. First, it binds to a GU-containing sequence at the 5’ end of the intron and to a branch point sequence containing an A towards the 3’ end of the intron. In a number of carefully-orches

 Core: Biology

C. elegans Development and Reproduction

JoVE 5110

Ceanorhabditis elegans is a powerful tool to help understand how organisms develop from a single cell into a vast interconnected array of functioning tissues. Early work in C. elegans traced the complete cell lineage and structure at the electron microscopy level, allowing researchers unprecedented insight into the connection between genes, development and disease. …

 Biology I
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