Fibrillin Proteins

Fibrillins are extracellular matrix glycoproteins that show a wide distribution in both elastic and nonelastic tissues and are integral components of 10-nm-diameter microfibrils. Fibrillin-1 is synthesized as profibrillin and is proteolytically processed to fibrillin. Wild-type profibril-lin is not incorporated into extracellular matrix until it is converted to fibrillin. The N-terminal region of each protein directs the formation of homodimers within a few hours after secretion, and disulphide bonds stabilize the interaction.[15] Dimer formation occurs intracellularly, suggesting that the process of fibrillin aggregation is initiated early after biosynthesis of the molecules. Fibrillin is posttranslationally modified by p-hydroxylation and N-linked and O-linked carbohydrate formation.[16] Baldock et al.[17] predicted fibrillin maturation from a parallel head-to-tail alignment. This model accounts for all microfibril structural features, suggests that intermolecular and intramolecular interactions drive conformation changes to form extensible microfibrils, and defines the number of molecules in cross section.

Fibrillin-1 and fibrillin-2 codistribute in elastic and nonelastic connective tissues of the developing embryo, with a preferential accumulation of the FBN2 gene product in elastic fiber-rich matrices. Mouse study of the developmental expression of fibrillin genes has revealed different patterns. Except for the cardiovascular system, in which Fbn1 gene activity is early and always higher than Fbn2, Fbn2 transcripts appear earlier than Fbn1 transcripts and accumulate for a short period of time just before overt tissue differentiation (i.e., a window of time immediately preceding elastogenesis). In contrast, the amount of Fbn1 transcripts increases at an apparently gradual rate throughout morphogenesis and is mainly expressed during late morphogenesis and well-defined organ structures. Furthermore, Fbn1 transcripts are predominantly represented in stress-bearing and load-bearing structures such as aortic adventitia, suspensory ligament of the lens, and skin. Thus spatio-temporal patterns of gene expression suggest distinct but related roles in microfibril physiology. Fibrillin-1 would provide mostly force-bearing structural support, whereas fibrillin-2 would predominantly regulate the early process of elastic fiber assembly.[18] Fibrillins could contribute to the structural and functional heterogeneities of microfibrils.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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