RESUMEN
This review will focus on the molecular organisation of the adult vitreous and how it undergoes ageing changes throughout life that result in vitreous liquefaction and a predisposition towards posterior vitreous detachment and retinal break formation. At birth, the vitreous humour is in a gel state due to the presence of a network of fine collagen fibrils. With ageing, these collagen fibrils progressively aggregate due to a loss of type IX collagen from their surfaces. The aggregation of collagen fibrils may cause vitreous liquefaction which, when combined with an age-related weakening of postbasal vitreoretinal adhesion, predisposes to posterior vitreous detachment. Throughout postnatal life, the posterior border of the vitreous base migrates posteriorly from the ora serrata into the peripheral retina. This is due to new collagen synthesis by the peripheral retina. This new collagen intertwines with pre-existing cortical vitreous collagen to create new adhesions and thereby extends the vitreous base posteriorly. If irregularities in the posterior border of the vitreous base arise from this process, there is a predisposition towards retinal break formation during posterior vitreous detachment and subsequent rhegmatogenous retinal detachment.
Asunto(s)
Envejecimiento/fisiología , Membrana Basal/química , Matriz Extracelular/química , Retina/química , Cuerpo Vítreo/química , Membrana Basal/metabolismo , Proteoglicanos Tipo Condroitín Sulfato/química , Colágeno/biosíntesis , Colágeno/química , Matriz Extracelular/metabolismo , Proteínas de la Matriz Extracelular/química , Fibrilinas , Proteoglicanos de Heparán Sulfato/química , Humanos , Ácido Hialurónico/química , Proteínas de Microfilamentos/química , Proteoglicanos/química , Retina/fisiología , Desprendimiento de Retina/etiología , Cuerpo Vítreo/anatomía & histología , Cuerpo Vítreo/fisiología , Desprendimiento del Vítreo/metabolismoRESUMEN
Human serum and the sera of a number of other mammalian species contain a naturally occurring macroglobulin with antibody-like properties which, in the presence of complement, is cytotoxic to murine Ehrlich ascites tumor cells in vitro. The serum of guinea pigs, rats and mice lack this macroglobulin activity but serve well as complement sources. The cytotoxic activity was demonstrated in short-term tissue cultures of Ehrlich ascites tumor cells by the marked and immediate inhibition of nucleic acid and protein synthesis. The cytotoxic activity is independent of the lytic antibody system which reacts against neuraminidase-treated lymphocytes.
Asunto(s)
Carcinoma de Ehrlich/inmunología , Proteínas del Sistema Complemento/inmunología , Inmunoglobulina M/inmunología , Macroglobulinas/inmunología , Animales , Anticuerpos Antineoplásicos/inmunología , Citotoxicidad Inmunológica , Femenino , Cobayas , Humanos , Técnicas In Vitro , Ratones , Conejos , Ratas , Especificidad de la EspecieRESUMEN
Insulin was enzymatically moniodinated with 127-I or 125-I, and an improved method of purification by anion exchange chromatography was employed. (127-I)Monoiodoinsulin was identified by spectrophotometric analysis and its molar extinction coefficient determined to be 6.31 times 10-3 M-1 cm minus 1. The observed specific activity of carrier-free (125-I)monoidoinsulin was close to the theoretical value (378mCi/mg). The monoiodotyrosyl residue of monoidoinsulin was shown to be solvent-exposed. The ionic properties of the substituted hormone were altered at pH values close to the pK of monoiodotyrosine (8.85), but the pI was unchanged (5.65). (127-I)Monoiodoinsulin formed rhombohedral crystals and co-crystallized with native insulin. Monoidoinsulin was indistinguishable from insulin with respect to binding to two out of three guinea pig anti-insulin sera, to binding to IM9 cultured human lymphocytes, and to binding to isolated rat hepatocyte plasma membranes. The potency of monoidoinsulin was not statistically different from that of insulin in the rat fat cell bioassay and in the mouse convulsion assay. An insulin-degrading enzyme extracted from rat liver degraded monoiodoinsulin less readily than native insulin; monoiodoinsulin was a competitive inhibitor of insulin degradation, and the Km values were 30 nM AND 78 NM for monoidoinsulin and native insulin, respectively. It is concluded that monoidination does not markedly alter the three-dimensional structure of the molecule and that only a few sensitive biological systems are able to distinguish the monoidinated from the native hormone.