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OBJECTIVES: To assess the suitability of a new anatomic model of the paranasal sinuses for endonasal surgical training. STUDY DESIGN: Prospective observational pilot study. METHODS: A new anatomic model of the paranasal sinuses was developed by the Department of Anatomy at the University of Zurich. The practicability of the model was evaluated by three experienced endoscopic sinus surgeons with a special focus on its possible use in training. Standardized surgical procedures were performed under simulated real-life conditions in the operating theatre. RESULTS: The endoscopic appearance of the nasal airway closely resembled real human tissue and the detailed anatomy of the model allowed the same structured surgical steps to be performed as in real life in the absence of bleeding. CONCLUSION: This anatomic model is a readily available teaching tool for endoscopic sinus surgeons.

UNLABELLED Mice homozygous for the mutation "nude" display a dysgenetic thymus (Pantelouris, 1968). The anterior mediastinum of these animals contains a rudimentary epithelial organ (pantelouris and Hair, 1970), which has been assumed to represent not a maldeveloped thymus, but rather a remnant of the parathyroid gland or of the ultimobranchial body (Wortis et al., 1971). We have investigated the development of the thymus in homo- and heterozygous nude by both light and electron microscopy. This paper describes the light microscopical findings in embryos and fetuses from the 11th up to the 18th day post conceptionem (pc). MATERIALS AND METHODS Homo- and heterozygous nude (nu/nu + nu/+) mice with the genetic background BALB/c were kept under specific pathogen-free (spf) conditions. Virgin nu/+ females were mated with nu/nu males. In addition, homozygous females were mated with homozygous males in order to investigate 11-day-old homozygous embryos. The embryos and fetuses were fixed in Bouin's solution and embedded in paraffin wax. Serial frontal sections (5mu) were stained with hematoxylin and eosin. RESULTS AND DISCUSSION Up to the 12th day pc, the thymus anlage of the n/nu embryo is indistinguishable from that of the nu/+ animal. The paired anlage develops from the epithelium of the ventral and dorsal diverticles of the 3rd pharyngeal pouch, and from the ectodermal vesicula cervicalis. In the nu/+ embryo, the thymic epithelium begins to proliferate between the 12th day and 13th day pc. In the central part of the anlage, the epithelial cells dissociate and begin to form a reticulum. At the same time, blood vessels from the surrounding mesenchyme invade the anlage. From the 14th day onwards, lymphoblasts are recognizable..

Binding and internalization of gold-labeled IFN-gamma (IFN-gamma/Au) by human Raji cells was examined by scanning and transmission electron microscopy. For SEM, visualization of gold particles was enhanced by the silver enhancement technique and by backscattered electron imaging. Binding studies revealed distinct labeling of microvilli-bearing cells after incubation with at least 10 U/ml IFN-gamma/Au, whereas cells with a smooth surface showed substantially lower labeling. After application of higher IFN-gamma (greater than 200 U/ml) concentrations, labeling intensity remained constant, which is consistent with the concentration of radiolabeled IFN-gamma required for saturating receptors on Raji cells. The specificity of IFN-gamma/Au binding was demonstrated by complete displacement with unlabeled IFN-gamma and by partial inhibition of labeling with a monoclonal anti-IFN-gamma R antibody. Thus, colloidal gold represents a valuable tag for visualizing the interaction of IFN-gamma with its receptor. Internalization of IFN-gamma/Au was initiated by accumulation of gold particles in coated pits which occurred within 10 min after warming of Raji cells. Additional incubation at 37 degrees C (up to 2 h) led to the appearance of gold particles in endocytic vesicles and lysosomes. Thus, our studies indicate that IFN-gamma/Au enters the Raji cells via the typical endocytotic pathway.

A variety of host cells, such as activated macrophages, natural killer (NK) cells, and polymorphonuclear leukocytes (PMNL), are cytotoxic for an array of non-antibody-coated tumor cells. Because such effector cells appear to use oxygen-dependent mechanisms to effect tumor cell destruction in certain systems, the possibility of an involvement of toxic oxygen species has been considered. To investigate whether interaction of effector cells with neoplastic cells induces the generation of reactive oxygen species, resting and activated rat macrophages and rat spleen cells (as a source of NK activity) were exposed to viable tumor cells of varied origin, and chemiluminescence was monitored. This sensitive indicator of reactive oxygen generation was stimulated only when tumor cells or culture supernatants were contaminated with mycoplasma. Mycoplasma-free tumor cells and culture supernatants were in no case able to trigger chemiluminescence in any of these effector cell populations. On the other hand, tumor targets were equally susceptible to killing by effector cells irrespective of whether mycoplasma were present. The data suggest that generation of chemiluminescence during interaction of natural cytotoxic cells and neoplastic cells is an artifact and that reactive oxygen species do not function as an effector mechanism in antibody-independent natural killing effected by activated macrophages and NK cells.

There is strong evidence that the immune response to Borrelia burgdorferi (Bb) contributes to the pathogenesis of Lyme disease. Bb are transmitted by ticks to the skin, which is particularly rich in dendritic cells (DC). The initial reaction of these APCs may already set the course to immune pathogenesis. To study the role of DC, biopsies from human skin were incubated with Bb and investigated in toto with electron microscopy. In addition, DC freshly isolated from dermis (DDC) and epidermis (Langerhans cells) were compared with blood-derived DC (BDC). In situ, Bb were found in the dermal layer of the skin only, occasionally cleared by DDC. Isolated DDC and BDC, but not Langerhans cells, readily engulfed Bb preferentially using coiling phagocytosis. Internalized Bb were located free in the cytosol and inside of phagolysosomes of DDC and BDC. Intravesicular Bb Ags were colocalized with MHC class II molecules. In addition, live Bb induced IL-12 production in BDC. Bb-pulsed BDC activated naive and primed autologous Bb-specific T cells, as measured by detection of granulocyte-macrophage CSF gene transcription and proliferative response, respectively. These data indicate that human DC phagocytose, process, and present Bb Ags. The way in which DC may influence the immune response in Lyme disease, however, remains to be evaluated.