Les corps myéloïdes de l'épithelium pigmentaire rétinien

Résumé La morphologie (forme, taille, structure) des corps myéloïdes de l'épithelium pigmentaire rétinien est décrite, ainsi que leur répartition chez les différentes classes de vertébrés. On définit les critères d'identification de ces corps: Ils ne sont jamais limités par une membrane, sont en continuité avec le reticulum endoplasmique lisse, sont formés de saccules aplatis, liés deux à deux par des complexes de jonction. Ils établissent des relations de continuité avec la membrane nucléaire. Les confusions entre corps myéloïdes et diverses autres structures (phagosomes en particulier) sont discutées. Il n'existe pas de corps myéloïdes dans la rétine des Mammifères.

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Myeloid bodies of the retinal pigment epitheliumI. Distribution, morphology and connections with cytoplasmic organels

Summary The morphology (shape, dimensions, structure) of the myeloid bodies of the retinal pigment epithelium and their distribution through several classes of vertebrates is described. The criteria of identity of these bodies are defined: They are never membrane-bounded, they are in direct continuity with the smooth endoplasmic reticulum, they are made of flattened discs linked two and two by junction complexes. They are in direct relation with the nuclear membrane. The confusion between myeloïd bodies and other structures, like phagosomes, is discussed. The retina of Mammals does not contain myeloïd bodies.

Chargé de recherche à l'INSERM. Travail réalisé grace à une subvention de l'INSERM.     

Extracellular release of photosynthetic products by freshwater phytoplankton populations, with special reference to the algal species involved

SUMMARY. Over three successive years, depth profiles of C-fixation and excretion, chlorophyll- a concentrations, phytoplankton species composition and bacterial numbers were determined in Lake Vechten, a slightly eutrophic lake in The Netherlands. Special attention was given to the method used to measure extracellular release.
Excretion of dissolved organic ¹⁴C depended largely upon the photo-synthetic activity of the phytoplankton, ranging from 0–2.5 mg m^-1 h^-1, representing a percentage extracellular release (PER) of 0–25%.
During a period in August, however, a subsurface chlorophyll- a maximum at 5–7 m depth coincided with high excretion rates of up to 10 mg Cm^-3 h^-1 (PER = 55%). Phytoplankton analysis revealed a stratification in numbers of Mallomonas caudata with a maximum at 5–7 m depth.
The results suggest that in these water layers bacterial populations grew at the expense of the dissolved organic carbon compounds excreted by Mallomonas caudata. This means that extracellular release can temporarily function as an important nutrient source for the heterotrophie community in addition to the more or less constant dissolved organic carbon pool.     

Studies on Fusarium-Gladiolus Interactions

Using standardized conditions, 65 genotypes of Gladiolus were screened for Fusarium resistance. High levels were found in 'large-flowered" types, Primulinus hybrids, G. callianthus, G. garnierii , and G. dalenii. Some accessions of G. dalenii exhibited no disease symptoms when inoculated with two standard test isolates. No resistance was found in 'small-flowered' types. To estimate race-specifity of the resistance, eight highly resistant Gladiolus genotypes were tested in an in vitro test against 43 isolates of F. oxysporum f.sp. gladioli. Two isolates were able to partially infect the G. dalenii accessions and this was confirmed using whole plants. Implications for resistance breeding are discussed.     

Discovery of potent inhibitors of receptor protein tyrosine phosphatase sigma through the structure-based virtual screening

Receptor protein tyrosine phosphatase sigma (PTPσ) has proved to be a promising target for the development of therapeutics for the treatment of neurological diseases. Here, we report the first example for a successful application of the structure-based virtual screening to identify the novel small-molecule inhibitors of PTPσ. These inhibitors revealed high potencies with the associated IC₅₀ values ranging from 0.1 to 1.3 μM and were also screened for having desirable physicochemical properties as a drug candidate. Therefore, they deserve consideration for further development by structure–activity relationship studies to develop therapeutics for neurological diseases. Structural features relevant to the stabilization of the newly identified inhibitors in the active site of PTPσ are discussed in detail.     

Nitric Oxide Synthase Regulates Growth Coordination During Drosophila melanogaster Imaginal Disc Regeneration

Mechanisms that coordinate growth during development are essential for producing animals with proper organ proportion. Here we describe a pathway through which tissues communicate to coordinate growth. During Drosophila melanogaster larval development, damage to imaginal discs activates a regeneration checkpoint through expression of Dilp8. This both produces a delay in developmental timing and slows the growth of undamaged tissues, coordinating regeneration of the damaged tissue with developmental progression and overall growth. Here we demonstrate that Dilp8-dependent growth coordination between regenerating and undamaged tissues, but not developmental delay, requires the activity of nitric oxide synthase (NOS) in the prothoracic gland. NOS limits the growth of undamaged tissues by reducing ecdysone biosynthesis, a requirement for imaginal disc growth during both the regenerative checkpoint and normal development. Therefore, NOS activity in the prothoracic gland coordinates tissue growth through regulation of endocrine signals.     

Ammonium photo-production by heterocytous cyanobacteria: potentials and constraints

Over the last decades, production of microalgae and cyanobacteria has been developed for several applications, including novel foods, cosmetic ingredients and more recently biofuel. The sustainability of these promising developments can be hindered by some constraints, such as water and nutrient footprints. This review surveys data on N₂-fixing cyanobacteria for biomass production and ways to induce and improve the excretion of ammonium within cultures under aerobic conditions. The nitrogenase complex is oxygen sensitive. Nevertheless, nitrogen fixation occurs under oxic conditions due to cyanobacteria-specific characteristics. For instance, in some cyanobacteria, the vegetative cell differentiation in heterocyts provides a well-adapted anaerobic microenvironment for nitrogenase protection. Therefore, cell cultures of oxygenic cyanobacteria have been grown in laboratory and pilot photobioreactors (Dasgupta et al., 2010; Fontes et al., 1987; Moreno et al., 2003; Nayak & Das, 2013). Biomass production under diazotrophic conditions has been shown to be controlled by environmental factors such as light intensity, temperature, aeration rate, and inorganic carbon concentration, also, more specifically, by the concentration of dissolved oxygen in the culture medium. Currently, there is little information regarding the production of extracellular ammonium by heterocytous cyanobacteria. This review compares the available data on maximum ammonium concentrations and analyses the specific rate production in cultures grown as free or immobilized filamentous cyanobacteria. Extracellular production of ammonium could be coupled, as suggested by recent research on non-diazotrophic cyanobacteria, to that of other high value metabolites. There is little information available regarding the possibility for using diazotrophic cyanobacteria as cellular factories may be in regard of the constraints due to nitrogen fixation.     

Monitoring occurrence,extinction, and colonization probabilities for gibbon populations

All gibbon species (Family: Hylobatidae) are considered threatened with extinction and recognized on the International Union for Conservation of Nature Red List of Threatened Species. Because gibbons are one of the most threatened families of primates, monitoring their status is now critically important. Long-term monitoring programs applying occupancy approaches, in addition to assessing occurrence probability, improves understanding of other population parameters such as site extinction or colonization probabilities, which elucidate temporal and spatial changes and are therefore important for guiding conservation efforts. In this study, we used multiple season occupancy models to monitor occurrence, extinction, and colonization probabilities for northern yellow-cheeked crested gibbon Nomascus annamensis in three adjacent protected areas in the Central Annamites mountain range, Vietnam. We collected data at 30 listening posts in 2012, 2014, and 2016 using the auditory point count method. Occurrence probabilities were highest in 2012 (0.74, confidence interval [CI]: 0.56–0.87) but slightly lower in 2014 (0.66, CI: 0.51–0.79) and 2016 (0.67, CI: 0.49–0.81). Extinction probabilities during the 2012–2014 and 2014–2016 intervals were 0.26 (0.14–0.44) and 0.25 (0.12–0.44), respectively. Colonization probabilities during 2012–2014 were 0.44 (0.19–0.73) and between 2014 and 2016 was 0.51 (0.26–0.75). Although local site extinctions have occurred, high recolonization probability helped to replenish the unoccupied sites and kept the occurrence probability stable. Long-term monitoring programs which use occurrence probability alone might not fully reveal the true dynamics of gibbon populations. We strongly recommend including multiple season occupancy models to monitor occurrence, extinction, and colonization probabilities in long-term gibbon monitoring programs.