Penetration and loading of human serum albumin in porous silicon layers with different pore sizes and thicknesses.

Human serum albumin was adsorbed into porous silicon layers with thickness up to 3 microm and with different mean pore radius in the range 4.5-10 nm. The adsorbed amount of protein was quantified by I(125) radioactive labeling techniques and ellipsometry. The results show that albumin penetrated into the pores when the mean pore radius was larger than 5.5 nm, but could not totally occupy the available surface area when the layer thickness was larger than 1 microm. Loading of albumin both into porous layers and onto plane silicon as a function of albumin concentration was also investigated. These measurements show that loading of protein increased with protein concentration at least up to 10 mg/ml for porous silicon and up to 1 mg/ml for plane silicon. The maximum deposition into the type of porous layers used here was 28 microg/cm(2), compared to 0.36 microg/cm(2) for plane silicon.

Size-dependent sex allocation in a simultaneous hermaphrodite parasite.

Most models of sex allocation distinguish between sequential and simultaneous hermaphrodites, although an intermediate sexual pattern, size-dependent sex allocation, is widespread in plants. Here we investigated sex allocation in a simultaneous hermaphrodite animal, the tapeworm Schistocephalus solidus, in which adult size is highly variable. Sex allocation was determined using stereological techniques, which allow measuring somatic and reproductive tissues in a common currency, namely volume. We investigated the relationships between individual volume and allocation to different reproductive tissues using an allometric model. One measure of female allocation, yolk gland volume, increased more than proportionally with individual volume. This is in contrast to the measure of male allocation, testis volume, which showed a strong tendency to increase less than proportionally with individual volume. Together these patterns led to sex allocation being strongly related to individual volume, with large individuals being more biased towards female allocation. We discuss these findings in the light of current ideas about size-dependent sex allocation in, primarily, plants and try to extend them to simultaneous hermaphrodite animals.

Quantitative study of intussusceptive capillary growth in the chorioallantoic membrane (CAM) of the chicken embryo.

In an attempt to sort out the respective contributions of sprouting and intussusceptive microvascular growth (IMG) during chicken chorioallantoic membrane (CAM) development, we analyzed the morphology and the quantitative growth of the capillary bed of the CAM by light microscopy. By perfusing the CAM microvasculature with highly concentrated colloidal gold particles, the capillaries could be unambiguously distinguished from the surrounding unlabelled tissue. This allowed us to identify, count and measure the intercapillary tissue profiles. By means of morphometric analysis we could show that CAM angiogenesis undergoes three phases of development. In an early phase, from Day 5 to Day 7, the major mechanism of capillary network growth is sprouting. In an intermediate phase, from Day 8 to Day 12, IMG is prevailing, and at Days 13 and 14, CAM structure is undergoing expansion with only a small increase in complexity. These findings are important in view of experimental protocols using the CAM as a model for testing angiogenetic factors. Indeed, care has to be taken not to misinterpret normal age-dependent alterations of the CAM vascular architecture as specific responses to tested agents.

Influence of zymosan (a non-specific macrophage stimulator) and of indomethacin on liver tumours--an experimental study in rats.

Zymosan--a non-specific macrophage-stimulating agent--reduces tumour take in the liver. The mechanism for this effect is not clear, but it may be mediated via the Kupffer cells and prostaglandins. On the other hand, the Prostaglandin-synthesis inhibitor, indomethacin, inhibits tumour growth. Pretreatment with zymosan (3 mg 100 g-1) for 3 days of two different strains of rats, inoculated in the liver with a hepatoma or an adenocarcinoma cell suspension respectively, reduced tumour take and also initial tumour growth. The effect on tumour take and initial growth was inhibited by concomitant administration of indomethacin (0.2 mg 100 g-1). When zymosan was administered after tumour cell inoculation the growth rate of the hepatoma was retarded, but this effect was not abrogated by indomethacin. Pretreatment with indomethacin had no significant effect on tumour take or initial growth. When given after the tumour was established in the liver, indomethacin reduced the growth rate of the hepatoma, but not of the adenocarcinoma. These results suggest that there are different mechanisms for the effects of zymosan on tumour take and on growth of an established tumour. In immunoincompetent nude mice the effect on the hepatoma was similar to the effect in the rat. In vitro both tumours were insensitive to zymosan and indomethacin. This study confirms that pretreatment with a non-specific macrophage stimulator (zymosan) diminishes tumour take and growth in the liver, that the effect of zymosan on tumour take in the liver is abrogated by indomethacin and that the zymosan effect on tumour take in the liver is at least partly mediated by the Kupffer cells and prostaglandins.