Sustained release of a model macromolecule from preparations with erodible core

A series of sustained release tablets were prepared which consisted of a water-soluble core and a highly hydrophobic coat. Release of a macromolecule, Spectrum Orange, from this preparation was studied. It was found that release was controlled by the coat composition and coating solution viscosity. SEM and optical microscopy of the tablets indicated that the coats contained pores on the surface which penetrated in towards the centre of the core. It was deduced that the almost zero order release of macromolecules from these tablets was basically through these pores and not by diffusion through the polymer matrix.

The electrophoretic mobilities of minerals determined by laser Doppler velocimetry and their relationship with the biological effects of dusts towards macrophages

The role of surface charge in the pathogenicity of mineral dusts has been little studied, partly due to the time consuming nature of such determinations using conventional microelectrophoresis apparatus. In this work the use of laser Doppler velocimetry proved to be a rapid method of determining the electrophoretic mobility of mineral dusts. Ceramic ball milling of fibrous minerals, whilst dramatically reducing the cytotoxicity of the dusts towards macrophages, had only a small effect on electrophoretic mobility. It is concluded that some other factor, possibly fibre morphology, is important for observed biological effects. The coating of quartz and kaolinite with poly-2-vinyl pyridine-N-oxide dramatically lowered their cytotoxicity towards macrophages. The dusts' electrophoretic mobilities were also lowered. The significance of these findings is discussed.

Adsorption of syndiotactic and isotactic poly(2-vinylpyridine 1-oxide) on quartz surface

Poly(2-vinylpyridine 1-oxide) inhibits the cytotoxic effects of quartz in cell cultures but the syndiotactic polymer behaves differently from the isotactic and atactic polymers. In each case approximately 1-0 mg/m2 of the polymer represents the adsorption maximum. No difference has been found between the adsorption isotherms of the stereoisomeric polymers or the stability of the adsorbed layers. The layers are not removed by repeated washing. The observations do not support the theory that the poly(2-vinylpyridine 1-oxide) is active because it coats the quartz surface.

[A method for the study of relations between the lung and the reticulo-endothelial system]

The experiments reported in this paper draw attention to three new facts : 1) the reticulo-endothelial system (RES) of normal Rat can be " filled " with a non toxic, polymeric substance, PVNO, which is taken up by macrophages by pinocytosis ; 2) a broncho-pulmonary irritation leads to a discharge of PVNO by the macrophage. The macrophages are poured out into the blood stream, whence they arrive in to the lung ; 3) this discharge of a polymer as PVNO which has been previously taken in the macrophage, can happen even 10-12 months after the filling of the RES by the macromolecule.