Comparaison de techniques de débruitage des images scintigraphiques

Scintigraphic images are strongly affected by Poisson noise. This article presents the results of a comparison between denoising methods for Poisson noise according to different criteria: the gain in signal-to-noise ratio, the preservation of resolution and contrast, and the visual quality. The wavelet techniques recently developed to denoise Poisson noise limited images are divided into two groups based on: (1) the Haar representation, (2) the transformation of Poisson noise into white Gaussian noise by the Haar–Fisz transform followed by a denoising. In this study, three variants of the first group and three variants of the second, including the adaptative Wiener filter, four types of wavelet thresholdings and the Bayesian method of Pizurica were compared to Metz and Hanning filters and to Shine, a systematic noise elimination process. All these methods, except Shine, are parametric. For each of them, ranges of optimal values for the parameters were highlighted as a function of the aforementioned criteria. The intersection of ranges for the wavelet methods without thresholding was empty, and these methods were therefore not further compared quantitatively. The thresholding techniques and Shine gave the best results in resolution and contrast. The largest improvement in signal-to-noise ratio was obtained by the filters. Ideally, these filters should be accurately defined for each image. This is difficult in the clinical context. Moreover, they generate oscillation artefacts. In addition, the wavelet techniques did not bring significant improvements, and are rather slow. Therefore, Shine, which is fast and works automatically, appears to be an interesting alternative.     

Le cycle de développement des Castes chezReticulitermes

Résumé La production des castes, notamment des nymphes, futurs imagos ailés et des ouvriers chez leReticulitermes lucifugus est soumise à un cycle biologique annuel. L'auteur montre que dans les colonies naturelles les nymphes apparaissent quelques semaines après l'essaimage des jeunes imagos, vers la fin du printemps en une fois et en grande quantité. Elles se développent pendant l'été et arrivent en automne à l'avant-dernier ou même au dernier stade avant la mue imaginale. En hiver le développement de la colonie est normalement arrêté par le froid. Au début du printemps les nymphes se transforment en imagos et quittent la colonie. Pendant le repos hivernal les sexuées femelles accumulent beaucoup de corps gras et, au moment où les grandes nymphes se transforment en imagos, une ponte massive se produit dans le nid. Après la disparition des imagos la colonie voit son potentiel nutritif considérablement augmenté, puisqu'il n'y a plus de nymphes à nourrir. Pour cette raison les larves, à leur tour bien alimentées, peuvent se transformer en nymphes. Celles-ci, par leur croissance et leur constant besoin de nourriture, abaissent de nouveau le potentiel alimentaire. En conséquence de cette baisse, les larves qui apparaissent pendant l'été et l'automne sont mal nourries et donnent des ouvriers.Si les colonies deReticulitermes l. santonensis ont leur nid dans une maison bien chauffée en hiver, comme c'est le cas dans quelques immeubles de La Rochelle, lecycle annuel peut se transformer encycle semestriel. Les nymphes formées au printemps arrivent à l'état imaginal en automne et essaiment alors. Quand ils quittent la colonie un nouveau cycle commence qui permet un autre essaimage cinq à six mois plus tard, au printemps.L'auteur suppose que le facteur climatique et le facteur alimentaire jouent le rôle principal dans la formation des nymphes et dans le cycle biologique des Termitières.     

Alcaloïdes de Zanthoxylum decaryi: la decarine,nouvel alcaloide dérivé de la benzophénanthridine

Four alkaloids have been isolated from the stem bark of Zatithoxylum decaryi. Three are known, dictamnine skimmianine, 4-methoxy-1- methyl-2-quinolone. The fourth decarine is new; its structure has been established as 9-methoxy-10-hydroxy-2,3-methylenedioxybenzophenanthridine.¹     

Cinétique de dégradation des hydrocarbures par Candida lipolytica

Résumé Le mécanisme d'assimilation des hydrocarbures par une levure, Candida lipolytica est étudié au moyen de l'analyse cinétique de la croissance du microorganisme et de la disparition du substrat hydrocarboné. Les hydrocarbures utilisés sont des n-paraffines. On ajoute au milieu soit un seul hydrocarbure (n-tetradécane ou n-hexadécane), soit un mélange binaire (n-dodécane et n-heptadécane), soit un mélange complexe (du n-undécane au n-octadécane). Contrairement à d'autres auteurs, nous pensons qu'il est peu probable que l'essentiel de la réaction s'effectue par contact des gouttes de substrat et des microorganismes puisque l'on observe des retards d'assimilation de certains hydrocarbures: ceux de faible poids moléculaire (les plus solubles) sont assimilés plus rapidement. Il semble donc que l'assimilation se fasse en grande partie à partir d'hydrocarbures préablement solubilisés.

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Kinetics of hydrocarbon assimilation by Candida lipolytica

Summary The mechanism of hydrocarbon uptake by a yeast, Candida lipolytica has been studied by means of the kinetic analysis of micro-organism growth and substrate assimilation. Hydrocarbons used as only source of carbon are normal alkanes either pure (n-tetradecane or n-hexadecane) or in mixture of two paraffins (n-dodecane and n-heptadecane) or eight paraffins (n-undecane to n-octadecane). In these last cases delays in n-alkanes consumption are observed. They show that the most soluble substrates (lower molecular weight) are first consumed. In opposition to other authors we think that there is little probability for main reaction occurring by direct contact between drops and micro-organisms. The evidence indicates that n-alkanes are mainly utilized in the dissolved state.

     

Activité cholinestérasique des corpuscules sensoriels cutanés de Herbst et de Grandry

Résumé L'activité cholinestérasique (ChE) a été étudiée dans les corpuscules de Herbst et de Grandry du bec de canard par la méthode de Karnovsky. Le BW 284 C 51, l'iso-OMPA et l'ésérine ont été utilisés comme inhibiteurs. Une activité cholinestérasique non spécifique (nsChE) a été identifiée dans les corpuscules. Elle est présente dès le début de leur différenciation.Corpuscule de Herbst: l'activité nsChE est localisée dans les cellules du bulbe interne (citernes périnucléaires, reticulum endoplasmique granulaire, vésicules associées à l'apppareil de Golgi) et à la surface de la membrane plaamique des cellules du bulbe interne et de la terminaison nerveuse.Corpuscule de Grandry: l'activité nsChE est localisée dans les cellules satellites (citernes périnucléaires, reticulum endoplasmique granulaire) et à la surface de la membrane plasmique des cellules satellites, des cellules de Grandry et de la terminaison nerveuse.Une forte activité nsChE a été mise en évidence dans certaines zones de contact entre les cellules dites sensorielles (cellules du bulbe interne et de Grandry) et les terminaisons nerveuses. Une réaction positive a été observée au niveau des mitochondries des cellules satellites et de la terminaison nerveuse du corpuscule de Grandry, et dans des vésicules du réticulum endoplasmique lisse des terminaisons nerveuses.Aucune activité ChE n'a été détectée dans les cellules capsulaires, les cellules de l'espace interne, les cellules de Grandry, et dans les vésicules synaptiques.Ces résultats ont été discutés en relation avec ce que l'on sait sur l'activité ChE des autres types de corpuseules sensoriels. La signification fonctionnelle de cette activité ChE et le problème de l'origine des différentes catégorics cellulaires qui constituent les corpuscules de Herbst et de Grandry ont été envisagés.

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Cholinesterase activity in the Herbst and Grandry cutaneous sensory corpusclesHistochemical study at the light and electron microscope

Summary Cholinesterase activity (ChE) was localized in the Herbst and Grandry cutaneous sensory corpuscle of the duck beak with Karnovsky's method. Controls with BW 284 C 51, iso-OMPA and eserine were carried out. A non-specific cholinesterase activity (nsChE) was identified in the corpuscles. This enzyme activity is present from the beginning of their differenciation.Herbst corpuscle: nsChE activity was localized in the inner bulb cells (perinuclear cisterna, granular endoplasmic reticulum, vesicles associated with the Golgi complex) and along the plasma membrane of inner bulb cells and nerve ending.Grandry corpuscle: nsChE activity was localized in the satellite cells (perinuclear cisterna, granular endoplasmic reticulum) and along the plasma membrane of satellite cells, Grandry cells, and nerve ending.A high nsChE activity was evident in certain zones of contact between the so-called sensory cells (inner bulb and Grandry cells) and the nerve endings. A positive reaction was seen in mitochondria of satellite cells and nerve ending for the Grandry corpuscle, and in smooth endoplasmic vesicles of the nerve endings.No ChE activity was detected in capsular cells, inner space cells, Grandry cells and in synaptic vesicles.These results are discussed in relation with what is known about ChE activity of other sensory corpuscles. The functional significance of this ChE activity and the problem of the origin of the different cells of Herbst and Grandry corpuscles have been considered.

     

Intérêt de l’analyse de la morphologie fine et de la qualité nucléaire des spermatozoïdes dans le cadre des techniques d’AMP

Routine semen examination does not identify minor malformations of the sperm nucleus and chromatin architectural defects, which may be associated with ART outcome and cannot be detected by the embryologist even at 1000x magnification. Recent publications have demonstrated the advantages, compared to routine analysis, of a new method of real-time detailed morphological evaluation of motile spermatozoa: motile sperm organellar morphology examination (MSOME). MSOME is performed with an inverted light microscope equipped with high-power differential interference contrast optics enhanced by digital imaging to achieve a magnification of 10000x. To be considered morphologically normal, a sperm nucleus must have both a normal shape and a normal chromatin content. The aim of the present study was to combine MSOME and sperm DNA fragmentation characteristics to assess reproductive outcome. The study population consisted of the male partners of 52 couples referred for conventional IVF or split cycles (half IVF-half ICSI cycles) and exhibiting normal routine sperm parameters. Spermatozoa were analysed by examining the fine nuclear morphology and DNA integrity using the sperm chromatin dispersion test (SCD test), based on the principle that the deproteinized nuclei of spermatozoa with nonfragmented DNA show extended halos of DNA dispersion that are either absent or only minimally present in sperm nuclei with fragmented DNA. Fertilization rates were significantly lower in the group showing less than 8% of normal spermatozoa according to MSOME criteria, but early embryo development was not affected. Fine sperm morphology correlated with DNA fragmentation rate. These results demonstrate that the assessment of sperm nuclear normality by MSOME analysis and SCD test improves characterization of the semen sample and should be evaluated as a tool for allocating patients to specific assisted reproduction treatments.     

Stabilité biologique des réseaux de distribution d'eau potable

The maintenance of the quality of water from the outlet of the treatment plant to the consumer tap is a major concern of water distributors. From a biological point of view, this maintenance must be characterized by a stability of biological features, namely bacterial growth from biodegradable organic matter, and protozoan bacterivory which must be not detectable. However, drinking water distribution systems are continuously exposed to a flow of biodegradable organic matter, which can represent around 20–30 % of the total dissolved organic carbon, and a flow of allochthonous microorganisms (bacteria, fungi, protozoa…), coming from the water treatment plant but also from incidents (breaks/repairs) on the distribution network itself. Apart from these microorganisms (heterotrophic bacteria in particular) can grow in this ultra-oligotrophic environment and colonize the all drinking water distribution system. The highest density of microorganisms occurs on the surface of pipewalls where they are organized in microcolonies (biofilm) that are mixed with corrosion products and inorganic precipitates. Five groups of organisms have been identified in distribution networks, in both the water phase and the biofilm: bacterial cells, protozoa, yeast, fungi and algae. The majority of these organisms are not pathogens, nevertheless potentially pathogen bacteria (Legionella…), fecal bacteria (coliforms, E. coli…), and pathogen protozoan cysts (Giardia intestinalis, Cryptosporidium parvum…) can transitorily find favorable conditions for their proliferation in the networks. Bacteria grow from the biodegradable fraction of dissolved organic matter while protozoa grow from dissolved organic matter, other protozoa but especially from bacterial prey items. The protozoan bacterivory was extensively studied in marine aquatic environments and in rivers, lakes,… but very rarely in drinking water distribution networks. Actually, proofs of the protozoan grazing on fixed and free-living bacterial cells were given by photography or film of biofilms accumulation on coupons that were previously immersed in potable water or by direct microscopic observation of bacteria in food vacuole of protozoa from potable water. A single and recent study has estimated protozoan bacterivory rate from laboratory experiences using fluorescent markers. It appears that in an experimental distribution system fed with biologically treated water (ozone/filtration through granular activated carbon), only ciliates present in the biofilm have a measurable grazing activity, estimated at 2 bacteria·ciliate⁻¹·h⁻¹ on average.Bacterial dynamics in drinking water distribution systems is complex and related to different parameters, like the biodegradable fraction of dissolved organic carbon, the presence of a residual of disinfectant, the nature and the state of pipewalls, the relative biomass of free and fixed bacterial, and grazing impact.The preservation of the biological stability of potable water during its storage in reservoir or its transport through the distribution systems can be achieved by (a) the use of chemical disinfectants (in particular by addition of chlorine) which is the widely used technique, or (b) the use of new techniques such as nanofiltration that can eliminate bacteria and significantly decrease the concentrations of organic matter at the inlet of the distribution network and in the potable water.

• (a)The use of oxidant, usually chlorine, induces a number of problems, in particular the development of oxidation by-products like trihalomethans (THM), among which some are recognized as carcinogenic products for animals. In addition, chlorine added at the outlet of treatment plant is consumed in the network and the maintenance of a residual of chlorine along an entire distribution network would need high concentrations of chlorine at the outlet of the treatment plant. This may be incompatible with standards for both residual chlorine and its by-products. Nevertheless, chlorine has a disinfectant effect on planctonic bacteria, if considering that only around 10 % of free bacterial cells are living cells, i.e. are able of respiratory oxidation. However, some studies show that bacteria fixed on granular activated carbon particles can be resistant to chlorine, as well as bacteria in aggregates. Thus, the addition of chlorine in potable water does not inhibit the formation of a biofilm at the surface of pipewalls. In the same way, protozoa transported by potable water can resist to chlorine.
• (b)The above disadvantages permitted the development of membrane filtration techniques like the nanofiltration, which is at the junction between reverse osmosis and ultrafiltration, and which seems to be an interesting alternative to conventional treatments because it presents the advantage to (i) decrease very strongly the concentrations of dissolved organic carbon (on average 90 % for DOC (Dissolved Organic Carbon) and 99 % for BDOC (Biodegradable Dissolved Organic Carbon)), (ii) to remove a very high proportion of almost the entire microorganisms (99 %), precursors of chlorination by-products, and micropollutans, (iii) to decrease the musty flavor of water (2-fold) and (iv) to produce a water that needs low concentration of chlorine.

     

Anticorps anti-spermatozoïdes: techniques de dépistage et interprétation des résultats

Since the first publication on the detection of sperm-agglutinating antibodies in infertile men, multiple assays have been described. The most useful tests are able to detect antibodies bound to the sperm membrane of motile spermatozoa. The immunobeads test (IBT) is considered to be the most advantageous in terms of its sensitivity, the low incidence of false-positive results, and its ability to localize antibodies of different immunoglobulin classes on the sperm surface. The IBT assay can be used in parallel with the mixed antiglobulin reaction (MAR), to detect sperm-associated antibodies in the ejaculates of infertile men, the most rational way to test for antisperm antibodies (ASA) in males. In view of the high level of agreement between the two assays, MAR, the easier of the two, may be used as a first step in the detection of these antibodies. A positive MAR must be confirmed by IBT, as this assay is more specific for the detection of IgA antibodies. The clinical significance of sperm-associated antibodies is usually established according to the proportion of motile spermatozoa coated with immunobeads, its class and its localization on the sperm surface. However, binding of immunobeads does not provide any information about the antigens against which the antibodies are directed. As the functional effects of sperm-associated antibodies may vary as a function of their antigenic specificities, other assays, using purified fertilization related antigens, are necessary to establish, for each individual, the specific impact of the antibodies on the fertilization process. The indirect IBT assay has recently become the most widely used test to detect the various classes of ASA in serum and cervical mucus of infertile women and in the serum and seminal fluid of infertile men, in combination with the direct assay described above. However, in most laboratories, it is performed with only one dilution of the biological fluid tested, usually a low dilution, so that antibody levels of no significance for fertility could be detected. This may explain a recente debate (Human Reprod, 1999) on the significance of ASA as a cause of infertility. At present, and in the absence of standardized assays able to identify the antigens involved in each individual immune reaction, antibody assays, as detected by the IBT assay, in the serum and/or genital secretions of infertile subjects might provide useful clinical guidance.     

Développement et évaluation d’un algorithme de segmentation automatisée des ventricules gauche et droit sur des images ciné d’IRM

An automated segmentation of the left and right ventricles on cine MRI is presented here. A rectangular region around the object of interest is defined in the original image, a morphological filter is then applied that combines openings and closings on connected sets, providing an image with homogeneous regions, which is finally segmented with an active contour model. The algorithm was tested on two databases with an expert's segmentation on the ventricles. One of the databases was provided by the Multicentric Initiative for a Platform of Evaluation in Cardiac Imaging (IMPEIC) group. Results show a very satisfactory correlation between the area (given in mm²) of expertise (x) and the area of automated segmentation (y) of the left ventricle (y = 1.00x + 8.6, r = 0.99). First results on the right ventricle show more than 83% similarity. The systolic phase proved to be more difficult to segment, which could be taken into consideration by introducing time regularization criteria in the algorithm.     

Périodes critiques de plasticité des cartes sensorielles corticales

Cortical sensory maps are topographically ordered projections of the peripheral sensory receptors. The size of the representation of different body parts is determined by the number of sensory receptors in the periphery, with substantial variations between species, even amongst closely related mammals. Maps can be modified during critical periods of development, as has been most thoroughly characterised in the visual and the somatosensory system. Recently the field has moved from a phenomenological to a molecular era: studies using mouse genetics demonstrate the importance of molecules such as neurotrophins and of neurotransmitters such as glutamate, GABA and serotonin for the developmental plasticity of these maps. Serotonin and neurotrophins acts on receptors that are transiently expressed on the thalamocortical axons. The radical changes in gene expression patterns that occurr during this period in both the thalamus and the cerebral cortex could underlie the time course of this very particular form of plasticity.     

Etude des premiers stades de développement de la Coccidie Coelotropha durchoni

Summary This study considers the earlier growth stages of Coccidium Coelotropha durchoni in its host, Nereis diversicolor. Before evolving into free trophozoites and gamontes in coeliac fluid, the parasites remain in muscular and coeliac cells in microscopic intracellular form. Electron microscope reveals that these stages show an intermediary fine structure between that of a sporozoite — from which they keep some typical characteristics such as the conoid, the fibers and the involuted tubuli — and that of the future free trophozoites. The wall consisting in two clear membrans is provided with one or several micropores. The classical cytoplasmic organites clearly stand out: dictyosomes show constant relationship with ergastoplasm, the mitochondria contain short inner tubuli. Besides the paraglycogen granules and lipoid vacuoles, at least three types of vacuoles may be observed. Peculiar topographic relationship connects mitochondria and paraglycogen granules probably in formation. In the nucleus with classical membrane and heterogeneous structure, a rather voluminous nucleolus may be seen.