RESUMEN
Magnetite nanoparticles coated with silica, obtained by a sol-gel process in the reverse micelle microemulsion, were characterized and homogeneously suspended in water in order to assay their biocompatibility toward blood cells, in view of a potential medical use of this material. Their hemolytic, pro-thrombotic and pro-inflammatory properties were observed.
Asunto(s)
Células Sanguíneas/efectos de los fármacos , Compuestos Férricos/química , Compuestos Férricos/farmacología , Nanopartículas de Magnetita , Dióxido de Silicio/química , Dióxido de Silicio/farmacología , Humanos , MicelasRESUMEN
Conversion of erythrocyte membrane protein 4.1b to 4.1a occurs through a non-enzymatic deamidation reaction in most mammalian erythrocytes, with an in vivo half-life of approximately 41 days, making the 4.1a/4.1b ratio a useful index of red cell age [Inaba and Maede, Biochim. Biophys. Acta 944 (1988) 256-264]. Normal human erythrocytes distribute into subpopulations of increasing cell density and cell age when centrifuged in polyarabinogalactan density gradients. We have observed that, when erythrocytes were stored at 4 degrees C under standard blood bank conditions, the deamidation was virtually undetectable, as cells maintained the 4.1a/4.1b ratio they displayed at the onset of storage. By measuring the 4.1a/4.1b values in subpopulations of cells of different density at various time points during storage, a modification of the normal 'cell age/cell density' relationship was observed, as erythrocytes were affected by changes in cell volume in an age-dependent manner. This may stem from a different impact of storage on the imbalance of monovalent cations, Na(+) and K(+), in young and old erythrocytes, related to their different complement of cation transporters.
Asunto(s)
Cationes Monovalentes/análisis , Envejecimiento Eritrocítico , Eritrocitos/química , Bancos de Sangre , Separación Celular , Tamaño de la Célula , Membrana Eritrocítica/química , Eritrocitos/clasificación , Humanos , Lactatos/análisis , Proteínas de la Membrana/análisis , Factores de Tiempo , Conservación de TejidoRESUMEN
Human erythrocyte band 3 becomes rapidly phosphorylated on tyrosine residues after exposure of erythrocytes to hypertonic conditions. The driving force for this phosphorylation reaction seems to be a decrease in cell volume, because (1) changes in band 3 phosphotyrosine content accurately track repeated changes in erythrocyte volume through several cycles of swelling and shrinking; (2) the level of band 3 phosphorylation is independent of the osmolyte employed but strongly sensitive to the magnitude of cell shrinkage; and (3) exposure of erythrocytes to hypertonic buffers under conditions in which intracellular osmolarity increases but volume does not change (nystatin-treated cells) does not promote an increase in tyrosine phosphorylation. We hypothesize that shrinkage-induced tyrosine phosphorylation results either from an excluded-volume effect, stemming from an increase in intracellular crowding, or from changes in membrane curvature that accompany the decrease in cell volume. Although the net phosphorylation state of band 3 is shown to be due to a delicate balance between a constitutively active tyrosine phosphatase and constitutively active tyrosine kinase, the increase in phosphorylation during cell shrinkage was demonstrated to derive specifically from an activation of the latter. Further, a peculiar inhibition pattern of the volume-sensitive erythrocyte tyrosine kinase that matched that of p72syk, a tyrosine kinase already known to associate with band 3 in vivo, suggested the involvement of this kinase in the volume-dependent response.
Asunto(s)
Proteína 1 de Intercambio de Anión de Eritrocito/metabolismo , Eritrocitos/fisiología , Soluciones Hipertónicas/farmacología , Tirosina/metabolismo , Animales , Proteína 1 de Intercambio de Anión de Eritrocito/efectos de los fármacos , Proteína 1 de Intercambio de Anión de Eritrocito/genética , Tamaño de la Célula/efectos de los fármacos , Citosol , Inhibidores Enzimáticos/farmacología , Precursores Enzimáticos/antagonistas & inhibidores , Precursores Enzimáticos/genética , Precursores Enzimáticos/metabolismo , Eritrocitos/efectos de los fármacos , Humanos , Péptidos y Proteínas de Señalización Intracelular , Concentración Osmolar , Monoéster Fosfórico Hidrolasas/antagonistas & inhibidores , Monoéster Fosfórico Hidrolasas/metabolismo , Fosforilación/efectos de los fármacos , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Proteínas Tirosina Quinasas/genética , Proteínas Tirosina Quinasas/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Estaurosporina/farmacología , Quinasa Syk , Factores de TiempoRESUMEN
The equilibrium interaction of doxorubicin and its N-acetyl derivative with a series of purine-pyrimidine alternating polydeoxynucleotides has been studied through spectrofluorometry to assess the relevance of the electrostatic contribution to DNA intercalation. The results have shown that: (a) the suppression of the positive charge on the aminosugar has: (I) a profound negative effect on the free energy of intercalation, as expected, and (II) a negligible influence on the base specificity, which supports the notion of an essentially electrostatic effect of N-acetylation on intercalation; (b) a reasonably good accord with the demands of a polyelectrolytic model, due to Friedman and Manning, is found.
Asunto(s)
ADN/metabolismo , Doxorrubicina/metabolismo , Doxorrubicina/análogos & derivados , Electricidad , Espectrometría de Fluorescencia , TermodinámicaRESUMEN
The chromophore-modified derivative of doxorubicin, 4-demethyl-6-O-methyl-doxorubicin, has been tested for antitumor activity in a range of experimental murine tumor systems. In contrast to the inactive 6-O-methyl derivative of daunorubicin, 4-demethyl-6-O-methyl-doxorubicin provided antitumor effects comparable to that of the parent compound. In addition, detailed DNA-interaction studies showed that the doxorubicin derivative retains the ability to bind DNA by the intercalation mechanism. However, the binding affinity was appreciably reduced following structural modification in the anthraquinone chromophore. On the basis of the proposed models of intercalation, these results could be rationalized in terms of steric influence of the bulky methoxy group. The results of this study are in agreement with the correlation already observed between DNA binding and relative antitumor activity of anthracyclines.
Asunto(s)
Antineoplásicos , ADN de Neoplasias/metabolismo , Doxorrubicina/análogos & derivados , Animales , Antineoplásicos/metabolismo , Antineoplásicos/toxicidad , Sitios de Unión , Supervivencia Celular/efectos de los fármacos , Doxorrubicina/metabolismo , Doxorrubicina/farmacología , Doxorrubicina/toxicidad , Femenino , Células HeLa , Cardiopatías/inducido químicamente , Humanos , Masculino , Ratones , Ratones Endogámicos C3H , Ratones Endogámicos DBA , Neoplasias Experimentales/tratamiento farmacológico , Relación Estructura-ActividadRESUMEN
Thermodynamic data relative to the reversible interaction between human or bovine serum albumin and some organic ligands (S- and R-warfarin, d- and l-oxazepam hemisuccinate, phenyl-butazone, fluorescein) in dilute aqueous solution were determined by means of gel permeation chromatography and microcalorimetric measurements. From an analysis of these data and on the basis of fluorescence titrations the identity of the "primary" binding site on the proteins for some ligands was evidenced, while in other cases a cooperative binding of two different ligands to different binding sites could be discerned.