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October, 2006
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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.

Defenses Against Pathogens and Herbivores

JoVE 11121

Plants present a rich source of nutrients for many organisms, making it a target for herbivores and infectious agents. Plants, though lacking a proper immune system, have developed an array of constitutive and inducible defenses to fend off these attacks.

Mechanical defenses form the first line of defense in plants. The thick barrier formed by the bark protects plants from herbivores. Hard shells, modified branches like thorns, and modified leaves like spines can also discourage herbivores from preying on plants. Other physical barriers like the waxy cuticle, epidermis, cell-wall, and trichomes can help resist invasion by several pathogens. Plants also resort to the production of chemicals or organic compounds in the form of secondary metabolites like terpenes, phenolics, glycosides, and alkaloids, for defense against both herbivores and pathogens. Many secondary metabolites are toxic and lethal to other organisms. Some specific metabolites can repel predators with noxious odors, repellant tastes, or allergenic characteristics. Plants also produce proteins and enzymes that specifically inhibit pathogen-proteins or pathogen-enzymes by blocking active sites or altering enzyme conformations. Proteins like defensins, lectins, amylase inhibitors, and proteinase inhibitors are produced in significant quantities during pathogen attack and are activated to

 Core: Biology

An Introduction to Caenorhabditis elegans

JoVE 5103

Caenorhabditis elegans is a microscopic, soil-dwelling roundworm that has been powerfully used as a model organism since the early 1970’s. It was initially proposed as a model for developmental biology because of its invariant body plan, ease of genetic manipulation and low cost of maintenance. Since then C. elegans has rapidly grown in popularity and is now utilized…

 Biology I

Fundamentals of Breeding and Weaning

JoVE 10293

Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN

Millions of mice and rats are bred for use in biomedical research each year. Worldwide, there are several large commercial breeding facilities that supply mice to research laboratories, but many facilities choose to also breed mice and…

 Lab Animal Research

The Cochlea

JoVE 10855

The cochlea is a coiled structure in the inner ear that contains hair cells—the sensory receptors of the auditory system. Sound waves are transmitted to the cochlea by small bones attached to the eardrum called the ossicles, which vibrate the oval window that leads to the inner ear. This causes fluid in the chambers of the cochlea to move, vibrating the basilar membrane.

The basilar membrane extends from the basal end of the cochlea near the oval window to the apical end at its tip. Although the cochlea itself narrows towards the apical end, the basilar membrane has the opposite geometry—becoming wider and more flexible towards the apical end. Primarily because of these physical characteristics, the apical end of the basilar membrane maximally vibrates when exposed to low-frequency sounds, while the narrower, stiffer basal end maximally vibrates when exposed to high frequencies. This gradient of frequency response creates tonotopy—a topographic map of pitch—in the cochlea. The hair cells are stimulated by the shearing force created by the vibration of the basilar membrane below them, relative to the stiffer tectorial membrane above them. Because of the tonotopy of the basilar membrane, hair cells are maximally stimulated by different frequencies depending on where they are in the cochlea. Those at the basal end respond be

 Core: Biology

Genetic Screens

JoVE 5542

Genetic screens are critical tools for defining gene function and understanding gene interactions. Screens typically involve mutating genes and then assessing the affected organisms for phenotypes of interest. The process can be “forward”, where mutations are generated randomly to identify unknown genes responsible for the phenotypes, or it can be…


Identification of Intracellular Signaling Events Induced in Viable Cells by Interaction with Neighboring Cells Undergoing Apoptotic Cell Death

1Section of Nephrology, Department of Medicine, University of Illinois at Chicago, 2Section of Nephrology, Department of Medicine, Jesse Brown Veterans Affairs Medical Center, 3Department of Biology, Kutztown University of Pennsylvania, 4Division of Rheumatology, Department of Medicine, Research Institute of the McGill University Health Centre, 5Department of Microbiology & Immunology, University of Illinois at Chicago

JoVE 54980

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