Skeletal Ultrastructure in some Tubuliporine Cyclostome Bryozoans

The ultrastructure of the calcareous skeleton is described in twenty–one species of recent tubuliporine cyclostome bryozoans, using field emission SEM. The succession of skeletal fabrics in interior walls may be classified into four different fabric suites. The first–formed part of the calcitic skeleton in all species for which it has been observed is a precursory fabric of tiny, wedge–shaped crystallites. This is succeeded in about half of the species studied by a fabric of transverse fibres, followed by foliated fabric and often semi–nacre (fabric suite 1). Most of the remaining species lack transverse fibres and have interior walls largely comprising semi–nacre (fabric suite 2). A few species have skeletons consisting of predominantly distally–oriented, irregularly or regularly foliated fabric (fabric suite 3). A single species has a skeleton of proximally–oriented foliated fabric (fabric suite 4). Basal exterior walls in all species have a precursory fabric of tiny wedge–shaped crystallites without a strong preferred orientation, deposited directly upon the organic cuticle, followed by a layer of planar spherulitic structure, which in turn is succeeded by a similar fabric to that developed in the interior wall of the species concerned. Outermost layers of frontal exterior walls exhibit one of the following combinations of three fabrics: an outer layer of (1) finely granular or wedge–shaped crystallites; a thin dense granular layer followed by (2) distally accreting planar spherulitic fabric., or (3) obliquely accreting planar spherulitic fabric growing partly towards the midline of the frontal wall. Terminal diaphragms usually have outer layers dominated by planar spherulitic ultrastructure with centripetal growth directions. The fabric suites present in tubuliporines encompass most known fabrics found in the other cyclostome suborders and support the notion that this species–rich suborder occupies a central position in cyclostome evolution.     

Pronase reduces intramembranous particle density in uterine epithelial cells in vivo

The proteolytic enzyme, pronase, was injected into the uterine lumen of rats. This treatment removed half the intramembranous particles (IMPs) from the apical plasma membrane of the uterine epithelial cells but tight junctions of these cells were unaffected. We conclude that at least some of the IMPs are proteinaceous in nature and suggest that IMPs not affected by pronase may be deeply embedded in the lipid bilayer.     

Stable isotopes in fish otoliths discriminate between lagoonal and oceanic residents of Taiaro Atoll (Tuamotu Archipelago, French Polynesia)

 The fully enclosed Taiaro lagoon is hypersaline (42.5 psu) and non-tidal; constant salinity and water level result from strong evaporation balanced by low percolation through the lagoon floor. Seawater can flow over the atoll rim during exceptionally high seas and may then replenish lagoonal communities with propagules of oceanic origin. The distinctive water chemistry of the lagoon suggests a possible way of identifying these immigrants. We established this potential by analysing stable isotopes of carbon and oxygen in the recent growth layers of otoliths of two adult reef fishes, Chaetodon ulietensis and Acanthurus triostegus, collected from both sides of the atoll rim. Fish from the two locations were discriminated by their isotopic signatures, suggesting that analysis of the microchemical signatures deposited during the larval development could be used in future work to determine which individuals and species complete their life-cycles in this unusual lagoon. Accepted: 28 August 1997     

Systemic delivery of an adenovirus expressing EBV-derived vIL-10 in mice infected with Schistosoma mansoni or Leishmania amazonensis: controversial effects on the development of pathological parameters.

Within the context of microorganism/host interactions, those which last over weeks are expected to be sensitive to more or less sustained and targeted immuno-intervention, such as delivery of cytokines known to operate as down-regulators of acute inflammatory processes. IL-10 has received growing attention as a potential tool in immunotherapy, due to its anti-inflammatory and immunosuppressive properties. Therefore, using two experimental models of long-term interactions between parasites and laboratory mice, we monitored some effects of the systemic delivery of an adenovirus (Ad) expressing EBV-derived IL-10 (vIL-10) designated Ad-vIL-10. We first monitored the vIL-10 serum level following intranasal, intraperitoneal, intramuscular and intravenous administration. The i. p. and i.v. delivery of Ad-vIL-10 allowed a high serum level of vIL-10 (= 100 ng/ml), the i.v. route leading to a more sustained expression (up to 3 weeks). As a first model of parasite/mouse interaction, Schistosoma mansoni/C57Bl/6 mouse was selected. Ad-vIL-10 delivery was performed 4 weeks after S. mansoni infection i.e. at the time of egg-laying, and several parameters were monitored: (i) number of adult worms in the mesenteric vein, (ii) number of eggs trapped in the liver and intestine, (iii) liver fibrosis, (iv) serum levels of egg-reactive antibody subclasses, (v) serum content of cytokines, and (vi) cytokine production in the supernatant of antigen-stimulated mesenteric lymph node cells. No apparent effect was observed, either on the different parasitological parameters or on fibrosis development at day 70 of infection. Surprisingly, a marked increase in both Th1 and Th2 type cytokines was observed in the sera of the Ad-vIL-10 injected animals, as well as in the supernatants of their Ag-stimulated mesenteric lymph node cells. Nevertheless, polarization of the humoral response towards a Th2 profile was demonstrated by an increase in the IgE level in the Ad-vIL-10-injected animals. As far as the second model is concerned, namely the Leishmania amazonensis /C57Bl6 mouse interactions, Ad-vIL-10 was delivered intravenously one day before subcutaneous injection of stationary promastigotes and footpad swelling was monitored over 110 days. Under these conditions, vIL-10 exhibited a biphasic effect, decreasing the lesion size at the early stages of infection, but leading to a more pronounced lesion size during the chronic phase. This observation suggests a deactivation of the macrophage host cells under the influence of vIL-10. The results are discussed in the context of immunotherapy and the paradoxical effects observed in immunointervention with vIL-10.