RESUMO
A bone-inductive protein has been purified from bovine bone and designated as osteogenic protein (OP). The purified OP induces new bone at less than 5 ng with half-maximal bone differentiation activity at about 20 ng/25 mg of matrix implant in a subcutaneous bone induction assay. The purified osteogenic protein is composed of disulfide-linked dimers that migrate on sodium dodecyl sulfate gels as a diffuse band with an apparent molecular weight of 30,000. Upon reduction, the dimers yield two subunits that migrate with molecular weights of 18,000 and 16,000. Both subunits are glycosylated. After chemical or enzymatic deglycosylation, the dimers migrate as a diffuse 27-kDa band that upon reduction yields two polypeptides that migrate at 16 kDa and 14 kDa, respectively. The carbohydrate moiety does not appear to be essential for biological activity since the deglycosylated proteins are capable of inducing bone formation in vivo. Amino acid sequences of peptides generated by proteolytic digestion show that the subunits are distinct but related members of the transforming growth factor-beta super-family. The 18-kDa subunit is the protein product of the bovine equivalent of the human OP-1 gene and the 16-kDa subunit is the protein product of the bovine equivalent of the human BMP-2A gene.
Assuntos
Família Multigênica , Proteínas/genética , Fator de Crescimento Transformador beta , Fatores de Crescimento Transformadores/genética , Fosfatase Alcalina/metabolismo , Sequência de Aminoácidos , Animais , Sequência de Bases , Matriz Óssea/metabolismo , Matriz Óssea/transplante , Proteína Morfogenética Óssea 7 , Proteínas Morfogenéticas Ósseas , Osso e Ossos/metabolismo , Bovinos , Cromatografia de Afinidade , Cromatografia em Gel , Cromatografia Líquida de Alta Pressão , Eletroforese em Gel de Poliacrilamida , Glicosilação , Substâncias de Crescimento/genética , Substâncias Macromoleculares , Peso Molecular , Osteogênese , Proteínas/isolamento & purificação , Ratos , Homologia de Sequência do Ácido NucleicoRESUMO
The ratio of mouth pressure developed 0.1 sec after occlusion at end-expiration (P0.1) to average inspiratory flow rate (VT/TI) has been proposed as 'effective inspiratory impedance', Imeff. We have studied a simple mathematical model of lung mechanics, consisting of an effective resistance, an effective compliance and a single pressure generator, to learn how Imeff is altered by changes in resistance (R), compliance (C), inspiratory duration (TI), and the degree of curvature of the inspiratory pressure wave form. The degree of curvature was varied between concave with respect to the time axis to convex and included a linear inspiratory muscle pressure function. Assuming a linear pressure function, we obtained an explicit equation for Imeff as a function of R, C, and TI. Using the same model we also studied the classical impedance as a function of R, C and frequency (of a sinusoidal excitation pressure). We found that Imeff was increased by increases in R, increasing degrees of concavity, decreases in C, and by decreases in TI. For this model the classical impedance was about 5 times larger than Imeff. Classical impedance was increased by increases in R, decreases in C, and decreases in excitation frequency. In conclusion, measurements of effective inspiratory impedance need to be interpreted in terms of R, C, TI, and the shape of the inspiratory muscle pressure function.
