Distribution et activités des alcaloïdes défensifs des Coccinellidae

From a survey of 30 species and varieties of ladybugs the presence of alkaloids appears to be correlated with the existence of aposematic colour and not with being carnivorous or phytophagous. The alkaloids described until now all belong to the Coccinellini and are closely related, but other types of bases have been detected in some genera. The observed distributions are in agreement with the modern taxonomy of the family.Ladybug alkaloids constitute an effective defence against ants, Myrmica rubra, and quails, Coturnix coturnix, but all the beetles containing alkaloids do not possess the same degree of protection. Individual quail react differently towards moderately protected species.The bioassay used for the first isolation of coccinelin is described. The repulsive activities of aqueous solutions of coccinellin and convergin towards ants have been compared.     

Stratégie d’étude des anticorps anti-nucléaires

Le terme d’anticorps anti-nucléaires (ANA), consacré par l’usage, est trop restrictif puisque certains de ces anticorps reconnaissent des antigènes cytoplasmiques. Un très grand nombre d’ANA a été identifié au cours des 30 dernières années. Seul un nombre restreint de ceux-ci est spécifiquement associé à des maladies précises, connues sous le vocable de connectivites. Toutefois, des ANA peuvent assui être rencontrés dans d’autres affections, un syndrome infectieux ou inflammatoire, une néoplasie, une maladie spécifique d’organe, en particulier les maladies du foie comme l’hépatite auto-immune et certaines cholangiopathies. Enfin, il ne faut pas oublier l’apparition d’ANA survenant lors de la prise de certains médicaments. La spécificité de ces anticorps est tout à fait différente de celle que l’on observe dans les connectivites.     

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.     

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.     

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.

     

L'erreur dans la détermination histophotométrique de l'acide désoxyribonucléique et la variation individuelle des noyaux en acide désoxyribonucléique

Sans résumé     

Les génotypes responsables de mucoviscidose ou d’absence bilatérale des canaux déférents ABCD

Over the last decade, the genetic basis for CBAVD has been identified by its association with CFTR gene mutations, and CBAVD is now generally considered to be a mild or incomplete form of CF. In this review, the author summarizes the main results of compilation of CFTR gene analysis conducted in French laboratories for 3,923 patients with CF and 800 males with CABVD. The degree of clinical expression can be affected by several variables, including the molecular mechanisms by which the various CFTR mutations impair or disrupt the function of the CFTR chloride channel. Phenotypic expression of CFTR mutational genotypes varies from severe, progressive pulmonary disease with pancreatic insufficiency (CF-PI), to mild pulmonary disease with pancreatic sufficiency (PS) or singleorgan forms of “CFTR-opathies”. In CF, a total of 310 different CFTR mutations accounting for 94% of 7,846 CF alleles have generated almost 500 different genotypes, comprising 2 severe mutations in 88% of cases (CF-PI), one severe mutation in trans to a mild mutation in 11% (CF-PS), and 2 mild mutations in 1% of identified genotypes. In CBAVD, 137 mutations scattered over the whole gene were identified in 60% of 1,600 CBAVD alleles during the study. Among the 150 characterized mutational CFTR genotypes, compound heterozygosity was the rule, and the most frequent CBAVD combinations were ΔF508/5T (35%), ΔF508/other mutation (30%, including ΔF508/R117H-7T: 5,6%), and 5T/other mutation (17%). No combination of two severe mutations was found in CBAVD (0%); by contrast with the CF population, 88% of genotypes identified in CBAVD comprised a severe mutation in trans to a mild mutation, and 12% consisted of 2 mild mutations. A total of 22 genotypes were shared by both CF and CBAVD. The role of the 5T allele as a splicing variant with variable, incomplete disease penetrance in CBAVD is reviewed. Other haplotype backgrounds, such as the TG12 sequence and the M470V polymorphism, may influence CFTR splicing and/or function. This study confirms the high molecular heterogeneity of CFTR mutations in CBAVD and emphasizes the importance of extensive CFTR analysis in these patients. Longterm follow-up studies of CBAVD patients are necessary in order to predict the phenotypic consequences of numerous CFTR mutational genotypes.     

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.     

L’évolution des premiers arbres : les stratégies dévoniennes

The earliest axes exceeding 10 cm in diameter, and presumed to represent small trees, evolved in the Middle Devonian (about 395 million years). They belong to the Cladoxylopsida, a basal group of ferns s.l. lacking leaves. These trees grow mainly vertically, the trunk producing short-lived branches at the top and adventitious roots at the base. They show a dissected vascularisation, and little if any secondary tissues. The Archaeopteridales that evolved at the end of the Middle Devonian, have leaves, abundant wood, and secondary phloem. Growth in the aerial and subterranean parts is tri-dimensional and extensive. Contrary to these two strategies that evolved several times independently during the history of terrestrial plants, that exhibited by the lycophytes became extinct at the end of the Mesozoic. These trees are characterized by a symmetrical development of the aerial and underground parts that branch dichotomously. Branch production by the trunk is relatively late. These trees show a narrow vascular system and a wide cortex.     

ForenSeek: un programme de simulation du développement des insectes nécrophages dédié à l’entomologie médico-légale

L’entomologie médico-légale repose sur l’utilisation des insectes nécrophages pour estimer le moment de la mort dans le cadre d’enquêtes judiciaires et permet dans certains cas de préciser les circonstances du décès. Cette technique repose sur des bases scientifiques solides et est désormais couramment utilisée en France comme à l’étranger dans le cadre d’affaires criminelles. Le projet ForenSeek est un outil informatique d’aide à la décision, dédié à la réalisation de simulations et d’expertises en entomologie médico-légale. Le cæur de ce programme est un modèle de comportement et de développement des larves de diptères nécrophages basé sur un système multi-agents (SMA). Ce procédé permet de modéliser des comportements de groupes complexes à partir de données individuelles simples, et est done particulièrement bien adapté à l’étude des populations d’insectes. De plus, les résultats de ce modèle sont destines à être traités automatiquement pour en extraire des informations sur la pertinence de chaque simulation, et ainsi estimer de manière automatisée et avec précision l’intervalle post-mortem (IPM).     

Intérêt potentiel des images paramétriques des temps d’éjection et de relaxation en tomoscintigraphie des cavités cardiaques dans l’évaluation des cardiopathies asynchrones

Intraleft dyssynchrony is strongly correlated to contractile dysfunction associated to severe heart failure. Dyssynchrony is also a predictive marker for cardiac resynchronization therapy response. We measured dyssynchrony values for both ventricles from gated blood pool SPECT images.Material and methodsThree groups of patients were sampled from normal patients (n = 7), mild heart failure patients (n = 24) and severe heart failure patients (n = 9). Time-derivative parametric images were obtained from 24-time bins gated blood pool SPECT data. We measured intraleft and interventricular contractile and relaxing dyssynchrony values from these images.ResultsIntraleft dispersions values linked to ventricular peak emptying rate were 107 ± 21 ms, 141 ± 58 ms and 515 ± 104 ms for each of the three groups. The values linked to left ventricular peak filling rate were 122 ± 62 ms, 219 ± 117 ms and 603 ± 164 ms respectively. Statistical significant differences (p < 0.01) were observed both for contractile and relaxing phases for severe heart failure patients. Mild heart failure patients had isolated statistical significant (p < 0.01) alterations of the ventricular relaxing phase. Correlation between isotopic dyssynchrony values and left ejection fraction led to a R square coefficient of 0.71 and 0.64 for time to peak emptying and to peak filling respectively. Correlation to QRS width values led to a R square coefficient of 0.76 and 0.62 respectively.ConclusionVentricular dyssynchrony correlated to the importance of the ventricular mechanical dysfunctions is a robust predictor of heart failure. Separate analysis of contractile and relaxing dyssynchrony may lead to a better understanding and characterization of the mechanical dysfunctions involved in heart failure.     

Les spermatozoïdes immobiles frais ou décongelés en fécondation assistée

Contrasting with sperm count or morphology, complete lack of mobile sperm may seriously impair ICSI fertilization and pergnancy rate. In three cases with flagellar skeleton abnormalities [dynein arm absence] only immobile sperm were found in the ejaculate. Following repeated ejaculations, higher rates of viable spermatozoa and even some motile spermatozoa could be found. Some times, in nonobstructive azoospermia, extensive sperm search didn't allow us to find but immobile sperm mostly, with very few motile sperm cells, not enough for the microinjection of all oocytes. The third group of immobile sperm is iatrogenic, following freezing and thawing surgically retrieved, testicular or epididymal spermatozoa in order to avoid repeated surgical retrieval. Following thawing, one find frequently very few motile spermatozoa that may be not enough for all retrieved oocytes and it might be necessary to inject some eggs with immobile spermatozoa. The outcome of ICSI using mobile and immobile sperm was compared in the three above mentioned groups: 1-immobile ejaculated sperm with flagellar defects, 2-immobile sperm discovered in the ejaculate after extensive sperm search and 3- immobile frozen-thawed testicular or epididymal spermatozoa. The results of ICSI in these groups show that fertilizing ability of fresh or frozenthawed immobile spermatozoa is not significantly different from ICSI with mobile sperm from the same origin. More over, in the first group with flagellar abnormalities, repeated ejaculations allowed us significantly increase sperm viability and fertilization ability. Finding only immobile fresh or frozen-thawed sperm the day of egg retrieval should not lead us to ICSI cancellation. Pregnancies may occur with such immobile sperm.     

Observations et discussions sur le développement embryonnaire des Phoronida

Resume La fécondation est généralement interne chez les phoronidiens. La segmentation des ceufs est totale, egale (parfois légèrement inégale) et de type radiaire (avec quelquefois une apparence fortuite de segmentation spirale). La gastrula est formée par embolie. La bouehe derive de la zone blastoporale sans formation d'un vrai stomodeum. L'anus est mis en place par perforation de l'ectodersme et représente une néo-formation indépendante du blastopore. Le mesoderme est issu par proliferation cellulaire des regions antérieure et laterales de l'archentéron. Le protoccele est forme par des cellules mésodermiques se disposant le long de la paroi du lobe préoral. Le métaccele est issu probablement suivant les espèces d'une ou deux masses. La formation du mesoderme correspond á une variation de la méthode entéroccelique typique. Les phoronidiens doivent être considérés comme des deutérostomiens, d'après l'ensemble de nos résultats (voir aussi Emig, 1973).

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Observations and discussions on the embryonic Development in Phoronida

Summary Internal fertilization (in metaccelom) generally occurs in Phoronida. The eggs are extruded to the exterior through the nephridia, shed freely into the sea-water or retained in the lophophoral concavity. The cleavage of phoronid eggs is total, equal (or subequal) and radial (with sometimes fortuitous appearance of spiral cleavage patterns). The gastrula is formed by emboly. The mouth is derived from the anterior remnant of the blastopore without a true stomodeum. The anus arises by perforation, as an independent structure of the blastopore. The mesoderm formed by budding originates as isolated cells proliferated from the anterior and lateral surfaces of the archenteron. In the preoral hood appears a protoccel by mesodermal cells lining the walls of the blastoccel. The trunk clom (or metaccel) of Actinotrocha originates from one or two posterior masses of mesodermal cells. It is possible that the mode of formation of this coelom varies in respect to the different species. The mesoderm elaboration is considered as a modified enteroccelous method.The acceptance of Phoronida as deuterostomes is regarded as the logical consequence of the present considerations (see also Emig, 1973): radial cleavage, origin of mesoderm by a derived enteroccelous method, trimetamerous actinotrocha.

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Abbréviations des figures a anus - lp lobe préoral - ar archentéron - b blastoccele - ma mésoderme de la région anterieure de l'archentéron - ml mésoderme des régions latérales de l'archentéron - bl blastopore - mes cellule mésodermique - bo bouche - n ebauche des - n éphridiesect mesderme - s sophage - end endoderme - p protocle - est estomac - t ebauche des tentacules - g ebauche du ganglion nerveux - te tentacule - gn glandes nidamentaire - v vestibule - i intestin     

Estimation du taux d’aneuploïdies des spermatozoïdes épididymaires prélevés en vue d’ICSI chez des hommes à caryotype normal

Over the last ten years, fluorescent in situ hybridization in decondensed sperm nuclei has been used to study the chromosomal constitution of human spermatozoa. Studies have estimated that the disomy rate per chromosomal pairs is between 0.15% and 0.3%. The aim of this study was to evaluate the aneuploidy rate of human epididymal spermatozoa extracted from five men with obstructive azoospermia undergoing IVF. Genetic studies (karyotypes, Y micodeletion syndrome and mutation of the CFTR gene) did not reveal any abnormality. Disomy frequencies were determined by X-Y-8 multicolour fluorescence in situ hybridisation on 18,013 epididymal spermatozoa and 20,000 spermatozoa from healthy donors (control group). No significant difference was found between epididymal and ejaculated samples. However, isolated non-significant differences were observed between one of the patients and the control group. In conclusion, the present findings suggests that there is no increased risk for de novo chromosomal aberrations after IVF therapy with epididymal spermatozoa of men with obstructive azoospermia.