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October, 2006
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Infection: Invasion of the host organism by microorganisms that can cause pathological conditions or diseases.

Combined In vivo Optical and µCT Imaging to Monitor Infection, Inflammation, and Bone Anatomy in an Orthopaedic Implant Infection in Mice

1Orthopaedic Hospital Research Center, Orthopaedic Hospital Department of Orthopaedic Surgery, David Geffen School of Medicine at University of California, Los Angeles (UCLA), 2PerkinElmer, 3Department of Dermatology, Johns Hopkins University School of Medicine, 4Department of Medicine, Division of Infectious Diseases, Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine

JoVE 51612



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

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

What is the Immune System?

JoVE 10895

The immune system comprises diverse biological structures and processes that protect the body from disease. These processes can be classified into innate and adaptive immunity. To work effectively, the immune system needs to detect pathogens by distinguishing the body’s own structures from foreign elements. If this determination fails, autoimmune diseases occur in which the immune system reacts against the body’s own tissue. The innate immune system is the first line of defense against infection. It comprises physical barriers and a variety of cells that act quickly and non-specifically against elements that are foreign to the host (i.e., non-self). Examples of physical barriers in mammals are skin, the lining of the gastrointestinal tract, and secretions, such as mucus or saliva. Once an invader overcomes physical barriers, cells of the inflammatory response are recruited to the entry site: mast cells release a plethora of chemicals that attract other cells of the innate immune system and activates the adaptive immune system. Phagocytic cells, such as neutrophils and macrophages, ingest and destroy pathogens. Natural killer cells, a special type of white blood cell, destroy virus-infected cells. Together, cells of the innate immune system eradicate the invader or hinder its spread, and activate the adaptive immune system. How can an organism

 Core: Biology

Viral Structure

JoVE 10822

Viruses are extraordinarily diverse in shape and size, but they all have several structural features in common. All viruses have a core that contains a DNA- or RNA-based genome. The core is surrounded by a protective coat of proteins called the capsid. The capsid is composed of subunits called capsomeres. The capsid and genome-containing core are together known as the nucleocapsid.

Many criteria are used to classify viruses, including capsid design. Most viruses have icosahedral or helical capsids, although some viruses have developed more complex capsid structures. The icosahedral shape is a 20-sided, quasi-spherical structure. Rhinovirus, the virus that causes the common cold, is icosahedral. Helical (i.e., filamentous or rod-shaped) capsids are thin and linear, resembling cylinders. The nucleic acid genome fits inside the grooves of the helical capsid. Tobacco mosaic virus, a plant pathogen, is a classic example of a helical virus. Some viruses have capsids that are enclosed by an envelope of lipids and proteins outside of the capsid. This viral envelope is not produced by the virus but is acquired from the host’s cell. These envelope molecules protect the virus and mediate interactions with the host’s cells. The viral capsid not only protects the virus’s genome, but it also plays a critical role in interactions with host cells. For i

 Core: Biology

Discontinuing Intravenous Fluids and a Peripheral Intravenous Line

JoVE 10278

Source: Madeline Lassche, MSNEd, RN and Katie Baraki, MSN, RN, College of Nursing, University of Utah, UT

Intravenous (IV) fluid administration and peripheral IV catheters (PIVs) may be discontinued for a number of reasons. The most common reason for discontinuing IV fluids is that the patient has returned to normal body fluid volume…

 Nursing Skills

Lytic Cycle of Bacteriophages

JoVE 10823

Bacteriophages, also known as phages, are specialized viruses that infect bacteria. A key characteristic of phages is their distinctive “head-tail” morphology. A phage begins the infection process (i.e., lytic cycle) by attaching to the outside of a bacterial cell. Attachment is accomplished via proteins in the phage tail that bind to specific receptor proteins on the outer surface of the bacterium. The tail injects the phage’s DNA genome into the bacterial cytoplasm. In the lytic replication cycle, the phage uses the bacterium’s cellular machinery to make proteins that are critical for the phage’s replication and dispersal. Some of these proteins cause the host cell to take in water and burst, or lyse, after phage replication is complete, releasing hundreds of phages that can infect new bacterial cells. Since the early 20th century, researchers have recognized the potential value of lytic bacteriophages in combating bacterial infections in crops, humans, and agricultural animals. Because each type of phage can infect and lyse only specific types of bacteria, phages represent a highly specific form of anti-bacterial treatment. This quality stands in contrast to the familiar antibiotic drugs that we often take for bacterial infections, which are typically broad-spectrum treatments that kill both pathogenic and beneficial bacteria. The w

 Core: Biology

What are Viruses?

JoVE 10821

A virus is a microscopic infectious particle that consists of an RNA or DNA genome enclosed in a protein shell. It is not able to reproduce on its own: it can only make more viruses by entering a cell and using its cellular machinery. When a virus infects a host cell, it removes its protein coat and directs the host’s machinery to transcribe and translate its genetic material. The hijacked cell assembles the replicated components into thousands of viral progeny, which can rupture and kill the host cell. The new viruses then go on to infect more host cells. Viruses can infect different types of cells: bacteria, plants, and animals. Viruses that target bacteria, called bacteriophages (or phages), are very abundant. Current research focuses on phage therapy to treat multidrug-resistant bacterial infections in humans. Viruses that infect cultivated plants are also highly studied since epidemics lead to huge crop and economic losses. Viruses were first discovered in the 19th century when an economically-important crop, the tobacco plant, was plagued by a mysterious disease—later identified as Tobacco mosaic virus. Animal viruses are of great importance both in veterinary research and in medical research. Moreover, viruses underlie many human diseases, ranging from the common cold, chickenpox, and herpes, to more dangerous infection

 Core: Biology
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