Collagen and Elastin

Resilin has a greater percentage of acidic residues than collagen, elastin, and silk fibroin and contains fewer non-polar residues (i.e., Gly, Ala, Val, He, Leu, Pro, Met, and Phe) than silk fibroin and elastin. The significant content of acidic residues might account for resilin s hydrophilicity as well as its low isoelectric point, as indicated through swelling experiments [141, 145]. Resilin contains little to no... 

Results of amino acid analysis performed on resilin from the locust Schistorcerca gregaria, compared with values for collagen, elastin, and silk fibroin. Reproduced from [145] with permission from Elsevier, copyright Elsevier 1961 Includes 106 hydroxyproline and 7 hydroxylysine... 

The major components of the ECM are the structural proteins collagen, elastin, and fibrihin a number of specialized proteins (eg, fibronectin and laminin) and various proteoglycans. 

Abstract Synthetic polymers and biopolymers are extensively used within the field of tissue engineering. Some common examples of these materials include polylactic acid, polyglycolic acid, collagen, elastin, and various forms of polysaccharides. In terms of application, these materials are primarily used in the construction of scaffolds that aid in the local delivery of cells and growth factors, and in many cases fulfill a mechanical role in supporting physiologic loads that would otherwise be supported by a healthy tissue. In this review we will examine the development of scaffolds derived from biopolymers and their use with various cell types in the context of tissue engineering the nucleus pulposus of the intervertebral disc. 

The pleural tissue is a typical connective tissue that consists mostly of matrix the fibrous proteins (collagen, elastin), and mucopolysaccharides, and a few scattered mesothelial cells, capillaries, venules, and ducts. Anatomists have defined several layers (Fig. 3.4) for each of the pleura. Layers 3 and 5 in Fig. 3.4 contain an abundance of fibrous protein, especially elastin. Both the interstitial (Layer 4) and mesothelial (1 and 2) layers contain capillaries of the vascular system and lymphatic channels. The matrix (ground substance) gives the pleura structural integrity and is responsible for its mechanical properties such as elasticity and distensibility. 

Although nonenzymatic glycosylation may affect practically every protein in vivo, it is likely that nonenzymatic browning will occur only in proteins that have a slow turnover or none at all, such as lens crystallins, collagen, elastin and proteoglycans. In some tissues, these proteins are, in effect, "stored" for a lifetime and undergo some characteristic changes, many of which have been observed in stored and processed foodstuffs (Table II). 

In the progressing lesion, a number of additional processes come into play, the most important of which are cellular necrosis with the release of foam-cell lipids to the interstitium, and the mitogen-stimulated proliferation of myointimal cells (smooth muscle cells), with the subsequent synthesis of collagens, elastin and proteoglycans. 

Baer, Hiltner, and colleagues (see Hiltner, 1979, and references cited therein) have used dynamic mechanical analysis to examine the hydration of collagen, elastin, and several polypeptides. A torsional pendulum constructed of the sample was examined for low-frequency (i.e., IHz) mechanical loss as a function of hydration and temperature. A common feature is a dispersion that is absent in the dry protein and appears at... 

The accelerated shedding of corneocytes disrupts the protective barrier function of the epidermis. From there, a cascade of secondary events stimulates growth in the basal layer of the epidermis and accelerates the conversion of keratinocytes into corneocytes" to restore optimum barrier function as soon as possible. Stimulation of the mother cells by the keratinocytes of the basal layer can unfortunately go hand in hand with reactional and inflammatory melanocyte stimulation, the cause of potential pigmentary changes. The stimulation of keratinocyte growth is also accompanied by positive stimulation of fibroblast proliferation and synthesis of proteins in the dermis (collagen, elastin and glycosaminoglycans)."... 

Proteoglycan aggregates are typically found in the extracellular matrix of connective tissue. The noncovalent attachment of each proteoglycan to hyaluronic acid via the core protein is mediated by two linker proteins (not shown). Proteoglycans interact with numerous fibrous proteins in the extracellular matrix such as collagen, elastin, and fibronectin (a glycoprotein involved in cell adhesion). 

Potassium in its ionic form, K+, is the most abundant positive ion in human and animal cells. As an electrolytic solution, K+ ions are pumped through the blood to all vital organs. Potassiums importance to the physiological system cannot be overstated It plays a crucial role in electrical pulse transmission along nerve fibers protein synthesis acid-base balance and formation of collagen, elastin, and muscle. 

Rubidium typically exists in the human body at the level of only 1/1,000 of 1 percent, and cesium content is even lower. Rubidium and cesium are both absorbed from soil by plants and are, therefore, present in small quantities in vegetables and up the food chain to meat products and humans. Rubidium is known to stimulate mammalian metabolism, probably because of its physical and chemical similarity to potassium, which plays a crucial role in electrical pulse transmission along nerve fibers protein synthesis acid-base balance and formation of collagen, elastin, and muscle. Its likeness to potassium may be the reason rubidium enhances growth in some plants. For particular insects, however, the introduction in the laboratory of rubidium to the bloodstream has been shown to drastically reduce fluid secretion and to change the electric potential across cell membranes. Excess rubidium is almost never encountered, however, in nature. 

Sometimes (18) the water molecules that fail to freeze on lowering the temperature are denoted as bound. This notion is open to criticism, however. It is true that collagen shares with other polymers the property that a considerable fraction of water remains unfrozen on lowering the temperature. On the basis of the number of grams of water per g of polymer the values are 0.5, 0.3 and 0.3 for collagen, elastin, and methyl-cellulose, respectively. For different reasons the polymer chains are essentially immobile. For collagen the crystalline, rodlike, molecules are apparently in close contact with each other and in elastin and methylcellulose the amorphous polymers are in the glassy state. At temperatures below 0 C ice is the stable phase in bulk. In the narrow, fixed, polymer interstices, however, space requirements are insufficient to form three-dimensional ice crystals. Other options available to the water molecules are to remain in the interstices in liquid form, or to form ice outside the polymer as a separate phase. 

We conclude that our dielectric results obtained for water absorbed in the rigid polymers collagen, elastin, and methyl-cellulose indicate that at room temperature the water molecules are rather mobile, that their mobility decreases at lower temperatures, until not separately, but collectively, they become immobilized in a glassy state in the range from 130 to 170°K. 

Figure 2. Thus, the heat capacity results for collagen, elastin, and methyl cellulose confirm the dielectric results that a glass point of absorbed water occurs near 150°K.

In vivo, cells have interactions with one another and their surrounding ECM. The ECM acts as a support network containing proteins such as collagen, elastin and laminin which gives the tissues their mechanical properties and promotes... 

I.-—Collagen,—Bony tissue is made up mainly of tricalcic phosjhate, combined with an organic material called oseein, which is a mixture of collagen, elastin, and au albuminoid existing in the bone-coUs. Collagen also exists in all substances which, when treated with H,0, under the in-... 

In rheumatic disease, the main pathological manifestations appear in connective tissue, the chief constituents of which are collagen, elastin and mucopolysaccharides. The last, apart from hyaluronic acid and chondroitin of cornea, are all sulphate esters , the sulphate groups of which are in a dynamic state with a short biological half-life. The sulphate exchange is under enzymic control and can be decreased in vitro and in vivo by corticosteroids " . Bostrom and Mansson examined the effects of a number of salicylates on the incorporation of S into calf costal cartilage slices in vitro. 

Fruit acids are an example of an active material. Also called alpha hy-droxyacids or AHAs, they have the abifity to penetrate the sldn, where they can increase the production of collagen, elastin, and intracellular substances thus improving the appearance of the skin. Thousands of cosmetic actives are used to affect the sldn in a variety of ways. They are used to tighten, tighten, and firm the sldn. They can be used to suppress perspiration as in the case of aluminum chlorohydrate. Salicylic acid and benzoyl peroxide are important ingredients because of their anti-acne activity (See Figure 7). Some active materials are added to sldn treatments to protect the sldn from the environment. Dimethicone and petrolatum are examples of sldn protectants. 

The skin is an excellent barrier to microbial and parasitic infections. The most superficial layer of the skin is composed of flattened squamous cells, which are highly keratinized. Beneath this is the epidermal layer composed of cells tightly interconnected by desmosomes and other intercellular structures. These, in turn, are attached to the basement membrane composed of covalently bound or interwoven macromolecules. Between the basement membrane and a target blood vessel is an extracellular matrix rich in type I collagen, elastin and proteoglycan. Elastin and type I collagen are both interwoven fibrillar molecules, whereas the carbohydrate-rich proteoglycan behaves like a hydrated gel. For details of these macromolecular interactions, the reader is referred to reviews on the structure of skin. 

These fibrous structural proteins are composed of repeating elements that form a linear structure. Collagens, elastin, and laminin are the principal structural proteins of connective tissue. 

Figure 10.1. Plot of GC levels of third codon positions against GC levels of second, first and first + second codon positions. A set of 1,380 human coding sequences was used. The solid lines are the orthogonal regression lines through the points, neglecting those surrounded by a broken line and corresponding to collagen, elastin and proline-rich protein genes. (From D Onofrio et ah, 1991).

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