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Western blotting is an important technique used in cell and molecular biology. By using a western blot, researchers are able to identify specific proteins from a complex mixture of proteins extracted from cells. The technique uses three elements to accomplish this task: (1) separation by size, (2) transfer to a solid support, and (3) marking target protein using a proper primary and secondary antibody to visualize. This paper will attempt to explain the technique and theory behind western blot, and offer some ways to troubleshoot.

We examined the impact of chronic stress on rat growth rate and intestinal epithelial physiology and the role of mast cells in these responses. Mast cell-deficient (Ws/Ws) rats and +/+ littermate controls were submitted to water avoidance stress or sham stress, 1 h/day, for 5 days. Seven hours after the last sham or stress session, jejunal segments were mounted in Ussing chambers, in which secretion and permeability were measured. Body weight (as a growth index) and food intake were determined daily. Stress increased baseline jejunal epithelial ion secretion (indicated by short-circuit current), ionic permeability (conductance), and macromolecular permeability (horseradish peroxidase flux) in +/+ rats, but not in Ws/Ws rats, compared with nonstressed controls. Stress induced weight loss and reduced food intake similarly in the groups. In +/+ rats, these parameters remained altered 24-72 h after the cessation of stress. Modulation of stress-induced mucosal mast cell activation may help in the management of certain intestinal conditions involving epithelial pathophysiology.

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There is increasing evidence that stress plays a role in the pathophysiology of chronic intestinal disorders, but the mechanisms remain unclear. Previous studies in rats have revealed that stress decreases gut barrier function and allows excessive uptake of luminal material. Here, we investigated whether chronic psychological stress acts to induce sensitization of intestinal tissues to oral antigens. Rats were subjected to 1 hour per day of water avoidance stress or sham stress daily for 10 days, and horseradish peroxidase (HRP) was delivered by gavage on day 5. Studies to determine sensitization were conducted on day 20. All stressed rats developed HRP-specific IgE antibodies, antigeninduced intestinal secretion, and increased numbers of inflammatory cells in gut mucosa. Luminal HRP was absorbed more readily by enterocytes of stressed animals. In addition, stressed rats had increased expression of interleukin-4 and decreased expression of interferon-␥ in gut mucosa, a cytokine profile that is typical of allergic conditions. Treatment of stressed rats with an antagonist to corticotropin-releasing hormone (previously shown to inhibit stress-enhanced gut permeability) eliminated the manifestations of intestinal hypersensitivity. Our results indicate that the presence of oral antigen during chronic psychological stress alters the immune response (to sensitization rather than oral tolerance) and causes subsequent antigen-induced gut pathophysiology. A number of publications 1-4 in recent years indicate that stress plays a role in gastrointestinal pathophysiology in conditions such as inflammatory bowel disease, irritable bowel syndrome (IBS), and food allergies. In inflammatory bowel disease and perhaps IBS, there is evidence that intestinal tissues may become sensitized to a luminal antigen and that subsequent encounter with the antigen initiates an inflammatory response that is involved in the pathophysiology of disease. [5][6][7][8][9] Although this theory remains controversial, it is clear that sensitization of intestinal tissues is a feature of food allergy. There is little information on the relationship between stress and intestinal anaphylaxis, although several reports indicate that psychological stress triggers allergic reactions in other organ systems.10 -12 With respect to detrimental reactions to oral antigens, immunogenic material must penetrate the intestinal epithelial barrier to contact and activate immune cells in the lamina propria. 13 In a sensitized host, immediate hypersensitivity reactions are initiated by antigen cross-linking of specific IgE antibodies bound to the surface of mucosal mast cells located in close proximity beneath the gut epithelium. Released mediators then act on nearby cells to induce both rapid (within minutes) changes in physiology and delayed (within hours to days) effects. 13,14 In allergic conditions in general, it is not clear how an individual develops sensitivity to a particular antigen. Genetic factors play a role, but persons can develop a hypersensitivity reaction ...

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