Uptake of microparticles by rat visceral yolk sac

Nanoparticles - known and unknown health risks

Manmade nanoparticles range from the well-established multi-ton production of carbon black and fumed silica for applications in plastic fillers and car tyres to microgram quantities of fluorescent quantum dots used as markers in biological imaging. As nano-sciences are experiencing massive investment worldwide, there will be a further rise in consumer products relying on nanotechnology. While benefits of nanotechnology are widely publicised, the discussion of the potential effects of their widespread use in the consumer and industrial products are just beginning to emerge. This review provides comprehensive analysis of data available on health effects of nanomaterials.

Fractionation of cells and subcellular particles with Percoll

At present, centrifugation is the most common method for separation and isolation of cells and subcellular particles. The technique can be used for a wide range of applications. During latter years it has become obvious what a powerful method density gradient centrifugation is, especially when used in conjunction with sensitive assays or clinical treatments. The most active areas for use of density gradient centrifugation include purification for in vitro fertilization of sperm of both human and bovine origin, isolation of cells for cell therapy of patients receiving chemo- and radiation therapy and basic research both on cellular and subcellular levels. These treatments and investigations require homogeneous populations of cells and cell organelles, which are undamaged after the separation procedure. Percoll, once introduced to reduce convection during centrifugation, has proved to be the density gradient medium of choice since it fulfills almost all criteria of an ideal density gradient medium. Recently good results have also been obtained after silanization of colloidal silica particles, e.g. BactXtractor. The latter medium has proved to be useful in recovery of microorganisms from food samples free of inhibitors to the Polymer Chain Reaction (PCR). The separation procedures described for Percoll in this review seem to be applicable to any cells or organelles in suspension for which differences in size or bouyant density exist. Furthermore, since Percoll media are inert, they are well suited for the separation of fragile elements like enveloped viruses.

Evaluation of the placenta: suggestions for a greater role in developmental toxicology

Both in human and in rat, two types of placenta are present: the yolk sac (YS) and the chorioallantoic placenta. Histiotrophy, alpha-fetoprotein synthesis and blood cell formation occur in YS of both species. Besides, the midgut, primordial germ cells and possibly immunological structures originate from the YS tissue. The specialised cells of the chorioallantoic placenta attach the embryo to the uterus and form the vascular connections necessary for the nutrient transport. The placenta redirects maternal endocrine, immune and metabolic functions to conceptus advantage. These complex activities are sensitive to direct toxicity. Indirect effects on the placental functions might be elicited by immunomodulators and endocrine disrupters. Some experimental models could be utilised to identify possible toxic effects on placenta. Among the in vitro models the rodent giant yolk sac culture may be used to study the transport of materials, morphological and/or biochemical alterations and biotransformation activity of the visceral YS epithelium. Other in vitro approaches utilise human derived trophoblastic cells and tissues to investigate implantation and perimplantation toxicology. Besides specific studies, in vivo reproductive toxicity tests could pay more attention to the evaluation of placental tissues. Nowadays, some physiologically based pharmacokinetic models for developmental toxicity are also available to describe the disposition of toxic substances and their metabolites during pregnancy in rodents. Thus, more detailed studies on the embryo-foetal placenta may provide an important tool to understand developmental toxicity mechanisms, with particular regard to embryolethality and delayed development.