Elastin from different tissues

B. Corn-position of Elastins from Different Tissues... 

In different tissues the microscopic and submicroscopic organization of elastica takes different and highly characteristic forms and it is of interest to speculate if this differentiation springs from differences in the chemical constitution of the elastin molecule or if it is induced by environmental conditions at the site of growth. Further constitutional studies on purified elastins isolated from the different tissues may help to resolve these questions. 

Little recent work has been reported on the water relations and sw elling properties either of native elastin or elastin that has been isolated by various procedures or treated with enzymes or hydrolytic reagents. This is to be deplored since the study of the hydration of a protein fiber is often a sensitive means of revealing the pattern of lateral bonds which lends structural stability. A comparison of the hydration of elastins derived from different animals, or different tissues of the same animal, would be particularly valuable since the methods are relatively insensitive to the preseruic... 

In contrast to milk, where samples are primarily derived from cows, meat analysis has to be performed in samples of a widely different animal origin including cattle, lamb, swine, poultry, and fish. Muscle is a complex matrix with a pH of 5.7, composed of muscle fibers, various types of connective tissue, adipose tissue, cartilage, and bones. Sarcoplasmic proteins such as myoglobin, and glycolytic enzymes are soluble in water while the myofibrillar proteins such as myosin and actin are soluble in concentrated salt solutions (14). The connective tissue proteins, collagen and elastin, are insoluble in both solvents. 

PMN Products - Neutral proteinases of PMN lysosomes degrade a wide variety of collective tissue substrates including elastin, proteoglycan, and collagen. Cathepsin G has been found only in PMN, and elastase from these cells has a substrate gpecificity different from that of pancreatic and macrophage elastase. In addition to their effects on connective tissue components, the neutral proteinases of PMN lysosomes also stimulate the activity of other cells involved in the inflammatory response. Both elastase and cathepsin G from human PMN stimulate the incor- poration of thymidine by human peripheral blood and splenic lymphocytes. The stimulated lymphocytes are of the B lineage, with no effect seen on T lymphocytes. 

Connective tissue, such as tendon and cartilage, differs from other solid tissues In that most of Its volume Is made up of extracellular matrix rather than cells. This matrix Is packed with Insoluble protein fibers and contains proteoglycans, various multladhesive proteins, and hyaluronan, a very large, nonsulfated GAG. The most abundant fibrous protein In connective tissue Is collagen. Rubberlike elastin fibers, which can be stretched and relaxed, also are present In deformable sites (e.g., skin, tendons, heart). As discussed later, the fibronectins, a family of multladhesive matrix proteins, form their own distinct fibrils In the matrix of some connective tissues. Although several types of cells are found In connective tissues, the various ECM components are produced largely by cells called fibroblasts. 

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