exam 4 front - 1. The injectable filler style of cosmetic...

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1. The injectable fil er style of cosmetic surgery is often used to hide wrinkles. It works by stretching the skin through the injected filler taking up space. Why might an equivalent mass of Restylane®, a brand name for hyaluronan or hyaluronic acid, have a greater “filler” effect than collagen? Be specific about any relevant molecular properties of these two ECM components. Hyaluronan is a long carbohydrate, which is less flexible than proteins and also fairly hydrophilic. This means it wil take up a lot of space due to its inflexibility and the attraction of water (which wil generate turgor). Col agen on the other hand is a rope-like protein. While somewhat inflexible as well, it is mostly insoluble so will not at ract water like hyaluronan does. So col agen should not take up as much space as hyaluronan would, making hyalyronan a better choice as a filler for wrinkles. 2. Skin is an arrangement of epithelial and connective tissues. While the specific strategies vary between these two tissue types, they work towards very similar goals. Describe one similarity between how both tissue types resist tension/pulling forces. Answers should include elements involved (intermediate filaments, collagen, fibronectin, etc) and reference BOTH tissue types. The following are the general comparisons: Both use rope-like proteins which are good at resisting pulling forces without breaking. In both tissue types the fibrous proteins are arranged in multiple directions in order to resist pul ing forces from multiple directions. In both cases the fibrous proteins are networked together to impart greater strength and stability (either between themselves or other proteins). 3. Integrins have both “inside-out” and “outside-in” functionality. Integrins are also important for both epithelial cells and the fibroblasts of connective tissue. Describe one function of integrins in either tissue type and explain if your function is an example of an inside-out or outside-in usage. Integrins are important for the organization of the basal lamina by epithelial cel s. They bind to laminins which in turn crosslink many of the ECM components that make up the basal lamina. This would be an example of outside-in since the integrins are serving to organize the ECM. The basal lamina can also act as a blueprint for regeneration. In this case, the ECM components in the basal lamina are acting as binding sites for migrating cells to attach to, and they fill in the available space. This would be an outside-in signaling event since the ECM is giving information to the cel s. In connective tissue integrins can bind to elements such as fibronectin to help organize the surrounding ECM. Binding al ows the cell to pull on fibronectin fibers and expose cryptic binding sites. This would be inside-out since the cel is using integrin binding to alter its outside environment.
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This note was uploaded on 12/30/2010 for the course BIO 320 taught by Professor Staff during the Spring '08 term at University of Texas.

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exam 4 front - 1. The injectable filler style of cosmetic...

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