Minnay Educational Services (www.minnay.com)assists students with supplemental study materials in terms of DVDs, Video, Audio, Software, WebAccess for Anatomy and Physiology, Microbiology, Pathophysiology, Pharmacology, Nursing and other medical related subjects.
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Anatomy and Physiology, Microbiology, Pathophysiology Videos
The Duke University Graduate Program in Molecular Genetics and Microbiology trains young researchers to solve fundamental problems in microbiology and genetics. Interaction with fellow students, faculty, and labs throughout the University is a hallmark of the program.
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Duke Graduate Program in Molecular Genetics and Microbiology
While the pathogen Chlamydia pneumoniae has been linked to asthma in the past, new research finds over two-thirds of people with severe asthma test positive for Chlamydia-specific antibodies, suggesting this antigen could be a good biomarker for detecting those at risk for asthma. Additional research finds that, in some cases, antibiotic therapy could improve asthma symptoms. Guest: Eduard Drizik, University of Massachusetts, Amherst
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Hot Topics in Diagnostic Microbiology: Chlamydia and Asthma
Tim Day, a Microbiology and Biochemistry Major, describes how his undergraduate solo project has turned into a patented work with larger clinical significance.
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Tim Day - Undergraduate Microbiology Research
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Microbiology Practice Test Chapter 1 part 2/3
Welcome message to Microbiology at NUI Galway. Our YouTube channel is based on our teaching and research themes of: 1.
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Welcome to Microbiology at NUI Galway
Download this song on iTunes at: itunes.apple.com http://www.pers.com - Animation of an amoeba under a microscope created for Apple Inc.
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Microbiology Movie
Nicole Gentile, PhD Candidate, provides an overview of basic microbiology and the concepts involved, including the bacterial growth curve and classifying organisms based on morphologies. This lecture describes blood, urine and skin/soft tissue cultures, focusing on the types of media, sample collection processes, culture procedures, as well as speciation and susceptibility testing. Basic staining procedures, such as the simple stain, gram stain, spore stain, negative stain, and acid fast stain are briefly discussed
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Structural characteristics. Graph provided.
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A song about the microorganisms we've grown to love Lyrics: Big spores keep on drifting Carry me to my new hosts skin Contact airborne isolation Its time to infect someone again I know its a sin Methicillin resistant staph aureus Vancomycin resistant enterococcus Multidrug resistant Tuberculosis MDR Klebsiella Sweet intestinal flora Stain them with methylene blue Clostridium difficile enterocoliits Lord, its coming after you Ventilator acquired Acinetobacter baumannii Only sensitive to Polymyxin A Intermediate sensitivity to piperacillin tazobactam Tigecyclines useless today Mississippi river valley Histoplasmosis capsulatum Blastomyces Dermatitidis Coccidioides immitis In the Southwest AIDS defining infections Cryptococcus Neoformans Mycobacterium Avium Complex Pneumocystis jirovecci Cytomegalovirus Toxoplasmosis, gondii Sweet intestinal flora Stain them with methylene blue Clostridium difficile enterocoliits Lord, its coming after you And it aint the flu Rickettsia Rickettsii Borrelia Burgdorfi Bartonella Henselae Rickettsia tsutsugamushi Nosocomial Pneumonia Living in the ICU Progressive Mutifocal Leukencephalopathy Lord its comin after you And youre screwed
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Microbiology has to do with things that are alive, but are too small to be seen with the naked eye. Learn about microbiology, bacteria and disease with information from a science teacher in this free video on physiology and the human body. Expert: Janice Creneti Bio: Janice Creneti has a BS in secondary science education and a BA in biology from Boston University.
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A typical day in the life of a Microbiologist. Courtesy of CareerOneStop Learn how to get there at http://www.MYCAREERRX.com College Educates. We Create Careers.
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Demonstration video showing how to perform a serial dilution on a liquid food sample (in this case raw unpasteurised milk).
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I shall explain the hybridoma technique used in production of monoclonal antibodies in a simplified way.
An antigen (unless it is a small peptide) is a complex molecule with several antigenic determinants (or epitopes). When the immune system encounters such an antigen, it is usually processed to result in several fragments. Humoral (antibody-mediated) response may occur against some of these fragments. There are multiple clones of B cell, each against a specific epitope; resulting in production of antibodies against several epitopes. Such a response is said to be polyclonal. This is what that happens when our body encounters a microbial antigen following infection or immunization.
There are situations when it becomes necessary to have antibodies against a single antigenic determinant produced by a single clone of B cell. Such a response is said to be monoclonal. In order to produce monoclonal antibody, it is necessary to possess a purified antigen.
Hybridoma technique was developed by Georges Kolher and Cesar Milstein in 1975, for which they were awarded the Nobel Prize. The chief participants of this technique are the B cells and the myeloma cells. The B cells are obtained from the mouse which has been immunized with the antigen of choice. Myeloma cells are malignant B cells that are immortal and multiply continuously. Myeloma cells that have lost the ability to produce antibodies are chosen for this technique. In addition, these cells lack the ability to produce hypoxanthine-guanine phosphoribosyl transferase (HGPRT-) and thymidine kinase (TK-) enzymes through an induced mutation. Normal B cells have functional enzymes (HGPRT+ and TK+) and are able to produce antibodies. However, their life span is not beyond two weeks. Hybridoma technique involves physical fusion of both these cells so that the resulting hybrid (called hybridoma) has the features of both these cell types.
The first step towards the production of monoclonal antibodies is the immunization of the animal by antigen of choice. Mouse is the commonly used animal, but rat or hamster too can be used. Following repeated immunization (booster doses) the blood of the animal is tested for antibodies against the immunized antigen. Once it is determined that the animal has produced sufficient antibodies, it is killed and its spleen removed. The spleen is rich in B cells and would contain B cells specific to the immunized antigen among B cells of other specificities. The B-cells are separated from other cells and cultured. They are then mixed with cultured myeloma cells and allowed to fuse. Fusions of the cells are aided by polyethylene glycol (PEG). Not all cells fuse; present in the reaction mixture are unfused B cells, unfused myeloma cells and fused hybridoma cells. The next step involves separation of hybridoma cells from the unfused cells using a special selective medium.
In order to understand the functioning of selective medium, one must be aware of the following facts. Multiplying cells need to produce their DNA. Most cells produce their purines nucleotides and thymidylate (both precursors of DNA) utilizing tetrahydrofolates by a De-Novo pathway. This can be blocked using anti-folate drugs such as Aminopterin. The cells can then adopt Salvage pathway to synthesize DNA if hypoxanthine and thymidine are exogenously supplied. Purine nucleotides are produced from hypoxanthine using hypoxanthine-guanine phosphoribosyl transferase enzyme and thymidylate is produced from thymidine using thymidine kinase. The selective medium (HAT medium) used to select the hybridoma contains aminopterin, hypoxanthine and thymidine. Amiopterin inhibits the De-Novo pathway and presence of hypoxanthine and thymidine facilitates salvage pathway.
Normal unfused B cells can’t produce DNA by De-Novo pathway because of aminopterin but are able to undertake salvage pathway. This is because they contain functional enzymes (HGPRT+ and TK+). However, since they are mortal, they die after few multiplications. Unfused myeloma cells too can’t use De-Novo pathway because of aminopterin. They are unable to utilize the salvage pathway either because of deficient enzymes (HGPRT- and TK-). These cells die despite being immortal. However, fused hybridoma cells receive (HGPRT+ and TK+) trait from normal B cells and immortality from myeloma cells. These cells can utilize salvage pathway for DNA synthesis and yet be immortal. After two weeks, only the hybridoma cells survive in the selective medium.
The surviving hybridoma cells would have formed against different epitopes. The next step is to select the hybridoma produced against the desired antigen. The cultures are diluted to such an extent that only a single cell gets transferred to the wells of microtitre plate. The cells are allowed to multiply. These cells produce antibodies that can be readily detected in their supernatant fluids. Supernatant fluids from all the wells are tested for antibodies against the antigen of choice and the well that contains desired antibodies is selected and the rest may be discarded. Finally, a hybridoma cell producing antibodies against the epitope of choice is available.
These hybridoma cells may be lyophilized, cultured in vitro or injected intra-peritoneally into a mouse and monoclonal antibodies raised whenever required.
Humoral immunity: How does the antibody production occur?
Depending on the nature of the antigen and the physiology of the individual, the immune response of the body to a foreign antigen may include only antibody production or a cellular response (T cell) or even both. It is still not very clear how the body makes this choice. Some antigens induce only an antibody response while others induce both humoral and cell mediated immunity. Sometimes, there are no apparent responses at all, yet in some cases these responses become exaggerated and harmful.
I shall concentrate only on humoral (antibody-mediated) response. Body responds to different kinds of antigens differently even with antibody production. Antibody production may be quick in some cases and delayed in other cases. Immune system may retain memory cells towards some antigen and none in case of some other antigens. Although the primary antibody response is IgM, some people produce IgE or IgG class of antibodies. It all depends on the body’s constitution and the immune response genes.
The cells that actually produce are the B cells and their derivatives, the plasma cells. In fact, most of the antibody production is by plasma cells and B cells produce only little. Plasma cells are derived from B-cell only after appropriate stimulation and activation of B cells. B cells are predominantly located in lymphoid organs such as bone marrow, spleen and lymph nodes. They may also be found in circulation, but their numbers are less compared to T cells.
Antigens can be classified into two types (T-independent antigens and T-dependent antigens) based on their ability to induce B-cell activation.
Some antigens have multiple repeating identical units; such antigens can bind to several receptors on the B-cell surface and effectively cross link them. B lymphocytes are not perfectly spherical cells as is often depicted; in fact their surfaces have long projections and have 106 numbers of receptors on their surface. These surface receptors are either monomeric IgM or IgG immunoglobulins. Their role is to bind with the antigenic epitopes. When an antigen such as flagellin, which has multiple repeating identical units, binds to many of the surface receptors, the receptors are said to be cross-linked. This is the first signal in B-cell activation. Apart from antigens cross linking the surface receptors, B cells have another mechanism of cross-linking surface receptors that involves immunoglobulin receptor and complement receptor. If an antigen that has C3d bound to it binds to surface immunoglobulin, another receptor (CR2) can bind with the deposited C3d on the antigen. This process too can cross link the surface receptors and activate the B cell. Upon activation by these signals, B cells undergo proliferation and start producing antibodies. Since there is no involvement of T cells in antibody production, these antigens are said to be T-independent. Antibody response to non-protein antigens, such as polysaccharides and lipids do not need participation of antigen-specific helper T cells. Since T cells have role here, the antibody production is typically quicker. An unfortunate effect of this response is that the immune system does not retain any memory of antibody production. Antibodies to T-independent antigens are mainly of low-affinity and responses are simple and mainly consist of IgG and IgM.
Humoral immune response to protein antigens is more complex; these antigens are said to be T-dependent as it requires participation of T cells for B-cell activation. Since the CD4 T lymphocytes stimulate B cells, they are called helper T cells. Antigen-specific CD4+ T cells recognize a protein antigen only when it is presented by antigen presenting cell (B cell, macrophage, dendritic cell etc) along with MHC class II molecules. B cells are also capable of antigen presentation to T cells. When an antigen binds to a specific B-cell through the surface immunoglobulin receptor, it is endocytosed by a receptor mediated endocytosis process. The processed antigen is then presented on its surface coupled with MHC II molecules for recognition by specific T cell. The initial encounter between the antigen-specific T cell and B-cell occur at the interface of the primary follicles and T cell area. Following this initial binding and the binding of other co-receptors (such as B7 of B-cell and CD28 of T cell, CD40 of B-cell and CD40L of T cell), the T cell also gets activated. Cytokines such as IL-2, IL4 and IL-5, which are secreted by activated helper T cell acts on B-cell to induce B-cell proliferation. Many of these B cell clones transform into effector cells called plasma cells and start producing antibodies. Within the lymphoid tissue, antibody secreting cells are found mainly in extrafollicular sites, such as red pulp of spleen and medulla of lymph node. These cells also migrate to bone marrow at 2-3 weeks after antigen exposure, and bone marrow becomes the principal site of antibody production. Antibody secreting cells do not circulate actively. Some of the Antibody producing cells that migrate to the bone marrow and live for several years, where they continue to produce antibodies even when antigen has been eliminated
The secreted antibodies have same specificity to the surface Ig receptor that captured the antigen. The antibodies that are secreted initially are predominantly of the heavy chain µ (IgM) isotype. In response to CD40 engagement and cytokines, some of the progeny of activated B cells undergo the process of heavy chain isotype switch. This leads to production of antibodies with heavy chains of different classes such as ? (IgG), ? (IgA) and ? (IgE).
Some of the antigen-activated B cells do not develop into antibody secretors. Instead, they acquire the ability to survive for long periods without antigenic stimulation. These memory cells are capable of mounting rapid antibody responses to subsequent introduction of antigen.
